Train app

15 minutes is plenty of time, just to reassure you. Be up and ready to get off your train (I have never taken a regionale train from Rome to Rome, so I am unsure of exactly the location and destination of the train you would be on, but Termini might be the end of its route) when it arrives, walk to the end of your track (where you would have to go anyway most likely unless you took the underneath walkways between tracks) and probably within about 30 yards you will see the board. It will be less than a 3 minutes' walk to 99% of bins. And even if you didn't need to look at the board, it would take you probably 45 less seconds to get to your correct bin.

Unfortunately I have never used the app, so I don't know how it would work. But also sometimes they don't have the binario assigned until very close to the time of the train. There is frequently the herd of people standing in front of the main board with all their luggage and then the RUSH to the binario to get on the train.

General tips for trains you might use, the pull through stations (I THINK Tiburtina is one? I think I have only ridden through there once or twice, never gotten off) have under-track passageways and you just go to the stairs to the "island" of your track, which are usually double-sided (like binari 2 and 3). The terminus stations, you have to walk ALL the way down to the end of the end of the track to get out (well, you can use some of the undertrack passageways if they are available, but usually you still have to get to the end to leave).

Don't know about the apps. But you have lots of time. The departure boards are always at the head of the platforms so easy to find and read. You should always know you train number. The board will show the end stop but not all of the in-between stops. ALWAYS check the boards. It doesn't happen a lot but the platform number is subject to change and I have seen it change within ten minutes of departure or arrival. And if you see a conductor, sometimes they will have that information. It is not hard and after a couple of transfers you will be fine.

Your friend is the page viaggiatreno.it or the info page on the trenitalia app for cell phones. If you know the train numbers, you can see where your train is and its expected arrival time and track, as well as the connecting train data (if your train is 10 minutes late, but the corresponding is 15 minutes late, your coincidence would be easier, for example). Probably you should better have a look in advance as it may be not easy to use; the web page is quite advanced, but for example traffic is divided in two sections (regional and long range) and you need a basic knowledge of lines topology. Infos are updated to the place a train was last seen (a PM is a posto movimento, a milepost in railway service without passenger service). In some cases info from this page has been invaluable to me, for example I managed to run to a connection at Bologna centrale in only three minutes, knowing exactly what I had to expect at arrival. There is a similar service for italo trains on the italo app.

Track assignments are not always reliable. For example, at Firenze SMN the track layout makes trains from north cross the path of trains from south and vv. - if a train is delayed, the predefined track assignments cannot be kept, this is why arrival tracks are announced only a few minutes before trains enter the station. (Trains to Siena and the coast do not cross paths and are much easier to dispatch). So, while there are websites with standard timetables and track assignments like e656.net, I advice you to use the app instead.

You can install the Trenitalia app - on the menu panel you will see the selection for the Departures and Arrivals Board - specify the station and you will be able to find both your arrival and departure tracks. Look at your trains for the current day to see an example.

From the Trastevere station you will most likely make your connection at Tiburtina. You can find a layout of the station from a simple web search.

Edited to add: And if you have time, taking the train over to Tiburtina a day or two in advance would give you a chance to scope it out.

Thanks for all the replies. I will adhere to yalls advice