Purchasing Rail tickets on Italian Rail

I'm sure some of our Italian members will soon furnish their excellent advice. In the meantime...

I'm not sure why you are averse to leaving from the Rome Termini station. It will certainly provide the greatest choice of trains. What website are you using? The Trenitalia site is showing frequent trains with only one change at the SMN station. Those are high speed freccias to Florence, then a Regionale to Siena. Looking at trips for next month, they were around €30. You can buy this from their website or app, or from a ticket machine (punch the button for English), or from a manned window at the station (Rome to Siena
doesn't really need a translation, on the rare occasion the attendant doesn't understand tourist English)

By the way, if you've been using Italia Rail, don't. Its not the train company. It's a 3rd part reseller.

Or for something different, you could take a direct Flixbus from the Autostatione Tiburtina for around €16.

I would suggest you take the bus rather than the train. We have done both. The train was just under 5 hours and the bus was 3 hours. Although from FCO the bus is between 3 1/2 hour to 4 hrs. There is a Flixbus that departs FCO at 1:30 pm and goes directly to Siena. If that does not meet your schedule the Flixbus from Tiburtina Bus Station to Siena provides more time options.

We have found that most all tickets agents speak English. When they do not, I use Itranslate or google translate on my phone.

Use the official train site
https://www.trenitalia.com/content/tcom/en.html

There is only one direct train to Florence from FCO at 1:53 pm
So you’d have to go thru Termini to Florence on a fast train then change to a regional

Or take the bus mentioned above-that is the best option

Siena is not on the main train line so it will always require changes to get there

Trenitalia publishes schedules about 6 mos in advance so you might want to wait until then before doing any more research. When time comes the best place to research trains is DB at https://int.bahn.de/en even though they can't sell you the ticket.

At this point you don't know when your plane will arrive since your carrier may change the flights, and because the flight may be delayed. If I was in your shoes I'd research train and bus times. Then when you land pick the best option. For trains it's probably unavoidable to go into Roma Termini. At the airport you can buy your ticket and since it will be on regional trains I believe there's no price discount for advance purchase. They have a staffed station at the airport and speak English, although learning a few polite phrases in Italian would be a good idea. Or you could put the Trenitalia app on your phone and purchase thru it. If your luggage is going to be a burden you may want to try to trim down what you bring although that's not always possible.

Seat61 suggests using Italiarail and has reasons:
https://www.seat61.com/train-travel-in-italy.htm#how-to-buy-tickets

Many thanks for the information provided.

Our flight is to arrive early, at 7:55am. Getting through immigration, etc. we could likely take a train around 9:30am.

The reason that I was trying to avoid going to the Rome central station was to avoid dragging luggage for a considerable distance to the next train. It is particularly tiring to my wife.

We had a recent trip to Germany and managed a trip from the Munich airport to nearby Augsburg using the Bayern Pass. We had success, but had to change trains in a hurry, find elevators in time for our connections and had to stand up for most of the trip.

As for taking the Flixbus I didn't find the directions to where to pickup the bus or buy the tickets. It has been a while since we have been through the Rome International Airport.

For Flixbus you buy on their website- put in Rome Fiumicono Airport to Siena. Tomorrow the first bus is at 1045. Bookings will not be open yet so far ahead.

Click on the details of the departure and you will see an icon like a book. Click on that and you get details of the departure point with a map. It is at Via Francesco Baracca, 00054 Rome Fiumicino Airport. Bus Station is located at the exit of Terminal 3 on the right