Train frecciarossa

You will first have to take the Leonardo express train from Rome airport to Rome Central train station, also called Termini.

The train leaves often, but from the time you buy your ticket till you step out at the train station in room could be an hour

And you need to add getting through the airport, baggage customs, etc.

It could work maybe but I would have a Plan B When I travel, I hate rushing, so I try not to make these tight connections.
Last time my plane from United States to Rome was two hours late

Hi, is your end point a hotel in Rome, or are you transferring in Rome to another city?

If you’re just going to a hotel in Rome, you can buy a Leonardo Express ticket for about €15, if your plane arrives early and you’re standing around. Or, you can take a taxi directly to your hotel (be sure it’s at the official taxi stand, NOT someone who approaches you to give you a taxi ride, or you will pay much more.)

This gives you details and photos for Terminal 3 and the train.

https://www.rome-airport.info/rome-airport-train.html

Where are you going on this train?
There is a direct train from FCO to Florence at 1:53- I’m wondering if that’s what you are booked on?

If so you can possibly make it but you never know if your flight is delayed or passport control takes long, etc.
Best advice is to wait til you land to book your trains.

The Leonardo Express runs continuously every 30 min so there’s really no need to pre book that

Let us know where you are going and we can give better advice

It’s dicey. An experienced travel agent should have recommended buying your Frecciarossa tickets once you are in the ground in Rome. That way, a late flight or a long line at Passport Control won’t matter. If the tickets are refundable, I’d ask for that and then book once you are at the airport and know you can safely make a train. To the larger cities (Florence, Milan, Venice, Naples) the trains run frequently throughout the day. What exactly is your destination that first day?