There is no direct train between Ciampino Airport and Rome. The airport doesn't have it's own train station so you need to go first in Ciampino town by bus and from there you can get the train to Roma Termini.
In Ciampino Airport, the bus stop is located just outside arrivals terminal. The journey to Ciampino Train Station takes about 5 minutes. The ticket cost 1.2 euro per person and can be purchased on board of the bus or from the ticket office inside the arrivals area. This service is provided by ATRAL/Schiaffini (www.atral-lazio.com)
From Ciampino Train Station there is a train every 10 minutes to Roma Termini and the journey takes about 15 minutes. A ticket cost 1.5 eur per person and can be purchased online from Trenitalia website, Trenitalia ticket offices or self-service machines inside the train station.
If you choose to buy the ticket from the self-service machines or ticket offices, be sure to validate your ticket by inserting it in one of the yellow stamping machines on or near the platforms.
If you choose to buy your ticket online please print the e-ticket and keep it with you when you travel. Trenitalia e-tickets are already validated.
1.5 euros per ticket, online or from ticket office