Transit

When are you planning to travel? The direct line between Milan and Paris was disrupted with a big landslide and that route is closed with no indication of when it will reopen. Unless you just want to go to MIlan, it might be better to fly from Rome to Paris.

In general for long distance routes, buy point to point tickets early, as soon as they go on sale, for the best prices. It will not be cheaper to but a pass...were you thinking a Eurail Pass? Go to Man in Seat 61 website ( www.seat61.com ) for excellent information on when a Eurail Pass might be worthwhile.

Just a question: have you purchased your flight already? You would save a lot of time by flying into Rome and flying back home from Paris.

The Rome to Milan train times and options are here:
www.trenitalia.com

Enter the Italian names for the cities: Roma and Milano

Update: Easy Jet flies from Milan to Paris in 90 minutes. Tickets are about $40.

I have a hotel in Milan for 1 week and want to travel back n forth to Paris from Milan . Then after Milan/Paris going to Rome for 1 week and site see local areas.
Flying in and out Rome FCO
Not planning to go until summer 2024
Need help with what is the best way to get around transit wise - which one to use and money information. Should I reserve ahead of time or wait till day of traveling .?
What is the cheapest to fly in and out , and what website ? Should I do 1 way into Paris n leave from Rome ? I have alerts already for when prices go up n down .

Bullet train is the name usually given to the high speed trains in Japan. High speed trains run in Italy by Trenitalia are Freccias. Those run in France by SNCF are called TGVs. They run according to schedules set by the respective train companies. Departure dates, times, and prices are on their websites. Advance purchase will give you the opportunity to buy a discounted ticket. But those tickets have restrictions- they are good only for the specific train, date and time, and are generally nonrefundable and not exchangeable. Purchases on the day of travel on long distance trains will be significantly more expensive. Eurail passes usually won't give you any saving, but you need to do the math yourself to see. Note that seat reservations are an extra cost not covered by eurail passes. To learn more about European train travel, read up on it on the Man in Seat 61 site linked above.

However I think your proposed itinerary involves a lot of unnecessary travel that is wasting both time and possibly money. Your itinerary requires intercity travel on 4 days to see 3 cities: Rome to Milan, Milan to Paris, Paris to Milan, Milan to Rome. You could visit the same 3 cities with only 2 travel days by simply flying into Rome and sightseeing there then taking the train to Milan for a week there, then taking a train or plane to Paris. Using a multicity flight ticket, you would fly into Rome and home from Paris. Or reverse this if the flights would be cheaper.

What you want is a multicity airline ticket. You could fly into Paris and home from either Milan or Rome.

Or you could do the reverse. I'd go to flights.google.com to check fares in both directions and to/from both the Italian cities. One direction may be cheaper than the other, and there could be a significant difference in the cost of using Milan vs. Rome as your international gateway.

Use the train between Milan and Rome. Both trenitalia.com and italotreno.it offer very fast service between those two cities.

It's the trip from France to Italy that's a bit difficult right now. The rail tunnel used by the fast trains between Paris and Milan has been damaged and is expected to be out of commission for a long time. I don't know how long that trip usually takes. When are you traveling?

Right now you can either travel through Switzerland (longer trip and more expensive) by train--in which case it would make sense to go first to Milan--or you can fly. If you opt to fly, you can fly either between Paris and Milan (and start or end your trip in Rome) or between Paris and Rome (and start or end your trip in Milan).

but going through Switzerland comes with its own difficulties. A few weeks ago a train derailed in the Swiss Gotthard tunnel, the main fast route through Switzerland between Milan and the north, causing the entire tunnel to be closed for repairs which will take many many months so all trains normally routed through there are cancelled and replaced by much slower trains using the congested old routes, along with all the trains carrying trucks which are routed onto trains for environmental and traffic reasons.

So going through Switzerland to avoid the direct route problems between Milan and Paris isn't a fast or easy fix.

I agree with my friends here on the forum. Since you are asking about flights, do look into multi-city either in to Paris and out of Rome or the opposite. In calculating costs, be sure to include the cost of train tickets onto the cost of flying in/out of Rome as well as how much time it will take from your sightseeing. The open jaw/multi city fare may be a little bit higher but if you calculate it out on paper it may still wind up cheaper.

For the long-distance tickets you will want to buy them ahead of time.

In looking at the official Trenitalia website, a direct train from Rome to Milan on Monday Oct 23 85.90 Euro.

A direct train from Rome to Milan at the same time (10:10 or so) on January 17 is 37.90E.

You can see it's much cheaper to buy tickets as far ahead as they are selling them. Book only thru the official train sites for Italy and France. Do NOT use one of the thinly disguised "travel agencies" to purchase train tickets.

DO read thru the Seat61 website. Here is the link to the information page for train travel starting in Rome.

https://www.seat61.com/international-trains/trains-from-Rome.htm

IF you have cell phone app skills, download the Trenitalia app along with the France SNCF app and use them for ticketing. It's very easy to retrieve your tickets from the apps and you don't need to validate a paper ticket.

I have a hotel in Milan for 1 week and want to travel back n forth to Paris from Milan .

How long do you plan to stay in Paris?

A 'multi-city' ( aka open jaw) ticket/itinerary from US-Paris, Rome-US ( or the reverse) would be something to consider.

Take train between Milan-Rome and fly ( on a standalone ticket) between Milan and Paris