Train arrival

We are taking a cruise in August that is ending in Venice Italy. We are planning on going back to Rome Italy for 1 week. What is the station in Venice (Cruise Port) and station in rome - we have rented a hotel on Via Brescio 5, Nomentano Rome. Also would we be able to bring our luggage on the train with us? If yes, what are the special seat numbers to book? Also what is estimate of price. We arrive in Venice on August 29th and plan to leave after 12:00 direclty after getting off ship.