Question about train in Rome

Arrive 30- 40 minutes before. There is no baggage check on the trains. The space is first come first serve or there is a door-to-door option for sending your bags from point to point rather than carrying it with you. It's called Bagaglio Facile, and the costs start at €20 for the first bag and €15 for the second. It's available to all travelers on Frecce trains, or anyone who has a CartaFreccia card.

Bagaglio Facile is only available Monday to Friday for most stations, although it operates on weekends in the cities of Milan, Rome, Florence, Venice, Turin, Bologna, Naples, Salerno, and Bari. Arrangements for Bagaglio Facile must be made by phone at least 24 hours in advance of your departure time.

https://www.italiarail.com/baggage

20 minutes is enough. The departure platforms are posted about 15 minutes before departure, before then you just have to stand around in front of the departure board. Train will arrive about 10 minutes before departure (longer than normal in Rome as the train changes direction).
As a "newbee" you might feel more comfortable with more time. 30 minutes would give you time to buy a sandwich.

"Should we check the suitcases?" - there is no check-in. All luggage must be carried on to the train and stowed in your coach by you.
There is some info about Frecciabianca trains here: https://www.seat61.com/Italy-trains.htm#Frecciabianca_
Plus more general stuff about Italian trains on the same page.

Chris and Jazz, thank you for the extra info and quick reply.

That was very helpful.

Mark

Chris is accurate. Sometimes a platform might be listed earlier than 10 or 15 minutes before but don't go the platform until about 10 mins before because sometimes the platform will change from an earlier posting. And it doesn't hurt to ask someone standing near the train or on the train if the train is going to xyz. Also you will have an assigned seat on that train so be sure to find the correct car prior to boarding.