fastest way to Cinque Terre from Rome? And late transportation within CT?

Several trains each day running from Rome's Termini to La Spezia, where you connect to regional rail service into CT. Takes about 4-1/2 hours with just the one stop. Trenitalia (Frecciarossa) leaving Termini around 12:00 gets you into town/s around 16:20, which we found perfect for check-in time at hotel. If you book early enough, they offer 'super economy' fares. Our discounted first-class seats were cheaper than if we purchased second-class on day of travel. Go figure.

Regarding hops between the CT towns, trains run pretty late, Midnight-ish in September. The ferries stop service around 21:30-22:00 (which wouldn't apply to Corniglia as there's no harbor in that town), but we found them ideal for getting between other towns and seeing landscape from the water.

Buon Viaggio !

Will there be late buses/trains that will let me get back to my room
is I choose to hang out until later in whatever town I'm in?

You'd have to check the train schedules for (specific CT village) > Corniglia but, as you probably know, you either have to get up to the tiny village on foot or via the little bus that runs between the station and top of the cliff. I believe the current (to Sept 11th) schedule is here; scroll down to page "Corniglia-Statione" on page 136-137. Looks like the last run from the station is at 7:40 PM. If traveling later in the month, reference the schedule nearer your trip for any changes.

https://www.atcesercizio.it/images/orari/Estate20212.pdf

I pulled the schedule from this page of the ATC website:
https://www.atcesercizio.it/index.php/it/variazioni-al-servizio/1330-libretto-orario
Click on "SCARICA QUI IL LIBRETTO ORARIO IN VIGORE DAL 9 LUGLIO, con il potenziamento del servizio nelle Cinque Terre."

I'd like to be double-checked that this site is what our OP should be using so, anyone, please jump in here if it's not right!
I loved Corniglia, wee as she may be. I'll bet its a sweet place to be in the evenings when the day-trippers are gone!

I'm planning on hiking each day to adjoining towns to explore

Andi, you know that the segment of famous "Blue" trail (Sentiero Azzurro) between Corniglia and Manarola is still closed, as is the segment of that trail between Manarola and Riomaggiore? There are ways around them but longer/more strenuous. Give a shout on a new thread if you need more info on hiking the park?

Kathy & Matt, thanks so much for the great info! The schedule will be very helpful, and I'll keep an eye on it as it gets closer to my visit to make sure it's up to date.

You're welcome, Andi. Just in case you haven't found the official website for the park yet, here it is:

http://www.parconazionale5terre.it/Eindex.php

It can be a little slow opening up so be patient. Let me know if you have trouble navigating it but this is one of the most important pages: shows the trail system, difficulty ratings and closures. Clicking on any of the lines (zoom in a bit) will bring up the trail number, descriptor, length and other info. A black line means the trail is closed.

http://www.parconazionale5terre.it/Esentieri-outdoor.php

Oh, and the CT Trekking or Treno MS card. If you plan to use the bus up/down from Corniglia, regional trains and hike the two open segments of the blue, you might want a Treno MS card. Individual tickets for regionale trains within the region (La Spezia > Levanto and villages in between) run about 4 euros a pop; I believe the bus fare from Corniglia Stazione up to the village is 1.50 one way but is covered by the card. They used to post the bus schedule for trips down to the station at the bus stop in the village - the bus has historically been timed to arrival of the trains - so you can reference that when you're there if they still do it.

Corniglia has two of the prettiest churches of the 5 villages, and a lovely little piazzetta (Largo Taragio) in front of one of them (Oratorio dei Disciplinati di Santa Caterina) for kicking back with a beverage and/or food from one of a couple of bordering restaurants/bars and doing some people watching. I'll assume they made it through the plague! :O)

Andi- The website RomeToRio has transportation solutions for travel. You just plug in what your travel is and it will give you multiple options.

Then use the official sites to check if Rome2Rio got it right.

LOL. The bus from Corniglia station to the village is a 3-minute or so hop that I'm pretty sure won't show up on rome2rio!

Editing to add: taking the Lardarina stairway DOWN to the train is fun, not as taxing as puffing UP the thing, and no bus to wait for so it's definitely an option, at least one way! :O)

Honestly, I'd just check on flights from Rome to Pisa and then take the train from Pisa and change in La Spezia. Or fly from Rome to Genova and take the train south passing through Portofino. I'll be in Monterosso at that same time. Corniglia would be the last town i would stay in due to the hundreds of stairs you have to climb from the train to the top of the town, but i am not a hiker, and do not know if it's easier to access the CT trails up in Corniglia. The regional trains between the towns used to stop at midnight, but i'm not sure if those hours are different since Covid. There is also a ferry that runs between the towns, but i just took a look at the ferry schedule and it doesn't look like they run past about 7pm and they do not stop in Corniglia. You can look up the schedule on incinqueterre.it and double check. Have you considered staying in a different town to accommodate the activities you'd like to do? Monterosso is a great base and my favorite, and Vernazza and Manarola are wonderful as well. There is a great wine bar in Monterosso that is great for people watching - Enoteca da Eliseo. And one in Manarola called Nessun Dorma. If you need other tips, let me know; I've been travelling to CT since 2000, (and these are my opinions only and may not be applicable to your trip). I'm more of a lay on the beach type!

Corniglia would be the last town i would stay in due to the hundreds
of stairs you have to climb from the train to the top of the town, but
i am not a hiker, and do not know if it's easier to access the CT
trails up in Corniglia

Melissa, as I'd posted above, there is a bus which travels from Corniglia's train station up to the village. Within the hours it runs, there is no need to climb the “Lardarina” stairway. Been there; done that!

I don't think it would be much, if any, more efficient to make the trip partly by air and partly by rail. Andi would have to get from Rome to the airport (if not doing this on the arrival day), and then would have to get from the airport in Genoa or Pisa to the train station for the last segment of the trip. I really wouldn't know how much to to allow for the air-to-rail connection in either city.

In addition, some of the air+rail routings involve an InterCity train for part of the trip. I believe those require seat reservations, which lock the passenger into a specific departure time. Trenitalia probably wouldn't be very flexible if the traveler missed an IC train because of a flight delay, whereas a delay on a train would be dealt with readily by allowing the traveler to take the next train.

Honestly, I'd just check on flights from Rome to Pisa and then take the train from Pisa and change in La Spezia. Or fly from Rome to Genova and take the train south passing through Portofino

I was not able to find any direct flights to Pisa.

Not sure getting to the airport to fly to Genoa then taking a train to CT, is better than a one change train trip from Rome. Certainly not cheaper, and if it is faster, its not any meaningful amount time

I don't think it would be much, if any, more efficient to make the trip partly by air and partly by rail

The odds are that You were right even before these time-wasting Covid procedures.

OT
I have just discovered, to my surprise , that there is a direct Intercity train departing daily from Roma Ostiense to Monterosso. Unfortunately it calls at Monterosso at 0:22, but it takes less than 5 hours.
/OT

Wow, Dario. I'd no idea about that direct train (Roma Ostiense> Monterosso) either.

I wouldn't take it, though. While there is a train to Corniglia from Monterosso at 00.22, there's not another until almost 5:00 AM so if the train from Rome is late at all... She'd also have to get up to the village (no bus running at that hour) and there's the chance of not being able to get into her accommodation in the middle of the night. The CT doesn't exactly operate 24/7!

Someone sleeping in a Monterosso hotel open till late could find that train useful. Even at 0:22 there is a distinctive lack of street Gangs in the area.

I just skimmed through the previous replies, so this may have been previously mentioned. In the same circumstances, I'd use a departure from Roma Termini at 09:57, arriving Corniglia at 14:29 (time 4H:33M, one change at La Spezia Centrale). That will get you to Corniglia at a reasonable hour so that you can get settled in your lodgings and then do a bit of a walkabout before dinner. There are numerous trains on that route, some with shorter travel times

On that short route, flying is not a good option due to the travel times involved to and from airports, security, check-in and the other usual hassles with flights.

Thank you all for so much for all the wonderful, helpful information. I really do appreciate it. Given all of this, I think what I'm going to do is book the Frecciargento 0625 am from Rome to La Spezia which only takes a little more than 3 hrs. Then I will catch the CTExpress to Corniglia. It will put me there early in the day, but I'll plan to sleep on the train and then stash my bags and walk/explore the town and area until I can check in. I'm still not sure about getting back after dark to Corniglia, but it does look like there is a late train from Montessero so it should be fine. I don't mind climbing the stairs if the buses aren't running but I did have a question - are taxis a thing in these small towns? I haven't seen much mention of them.

I'll plan to sleep on the train and then stash my bags and
walk/explore the town and area until I can check in.

Hmmm. Will your accommodation store your bags until check-in? Just asking as it's a REALLY tiny village that, last I knew, didn't have public storage service. Do be careful to keep your valuables (passport, cash, credit cards, phone etc. ON you while sleeping on the train, OK? And don't forget to validate your CT express train tickets before boarding! If buying the CT Trekking or Treno card in La Spezia, you only have to validate it once, to start the clock ticking on it.

Good thought, Kathy. I just sent them a message. I will only have one small bag, so hoping they will do that for me.
I've been warned about the train, and am pretty good at draping myself around my luggage and my luggage around me. I once slept on top of my suitcases in an airport in Ethiopia :) Also, my medical background taught me to 1. be able to sleep anywhere 2. be a very light sleeper. But I do appreciate the advice!
Any experience with taxis?

...in an airport in Ethiopia

Pish. The CT will be a walk in the park then!
No experience with CT taxis but hopefully someone else does.

andi,

I haven't really noticed the taxi situation in the other towns, but Monterosso has at least a few taxis. I typically use a taxi to get from the rail station to my hotel in the "old town" as it's a bit of a walk and partially uphill. As there are only a few, you may have to wait for one.

Then I will catch the CTExpress to Corniglia

If you find a way to purchase also this ticket online, you save the time needed to time-stamp. Online sales close 15 minutes before the departure time of trains, so you can minimise risks depending on a late train from Rome.

Thank you for the taxi info. It would be a last resort, but good to know it's an option. I'll look into the online CT Express ticket, too. Maybe I can get it while purchasing my CT Pass

If buying the CT Trekking or Treno card in La Spezia, you only have to
validate it once, to start the clock ticking on it.

In hindsight, I didn't word this clearly.
The trekking card is ONLY for hiking the trails in the CT which you need it for; pretty much JUST the open sections of the Blue Path. It doesn't cover transport. The treno card covers both trails + regionale train and local bus, like the one from the Corniglia train station up to the village. That treno card is the one you need to validate before boarding a train.