Gillian & DarrylM,
Gillian: Is there a reason you want to take a taxi? The train station is very nearby and the trains are frequent.
They go to the Termini - main station in Rome and you can always do a taxi from there.
DarrylM: I agree with the other poster...Take the train and save 200 euros....It's about 25 Euros and will take you to the main train station in rome. You can google italian train and you will find the main italian train line.
It's time for a reality check, folks!
Leonardo da Vinci Intrnational Airport (FCO) is in Fiumicino, which actually is closer to Civitiavecchia than to Roma. The cab fare from the airport to Roma is about ninety (90) euros. It makes absolutely no sense whatsoever to take the train to Roma from Civitavecchia if you want to go to the airport.
The cruise line's transfers may well be the most economical transportation from the pier to the airport for two people.