My first thought is to stay in Rome instead of the airport hotel, If you have not prepaid for that hotel, please consider a hotel in Rome. You will be able to enjoy the city in the evening and have extra time for sightseeing during the day and a half. There is nothing more dismal than an airport hotel in the evenings. There are many posts on this board on the subject. Look at the Rome hotel thread for ideas.
Here are a couple:
https://boards.cruisecritic.com/topic/2882786-late-nite-arrival-to-fco-for-ncl-cruise-next-day/page/2/#comment-64054438