Italy's Italo train debuted April 28 2012. Nowadays it connects Rome with Milan, Venice, Bologna, Florence, Naples and other cities more. It's being billed as the most advanced train in Europe. It is basically a high class train, not actually cheap, but if you book in advance you can get some interesting offers (usually no change-no refunds). Checking both Trenitalia and ItaloTreno to find the best schedule or the best offer is good advice.

In Rome, most trains of ItaloTreno serve the stations Roma Ostiense and Roma Tiburtina, just a few leave from Roma Termini. No problem: both Ostiense and Tiburtina are easily reachable by metro line B (stop Piramide for Ostiense, stop Tiburtina F.S. for Tiburtina).