I also take it that you have at least an overnight in Rome before departing on your cruise. While you have plenty of time for your current connection, things do go wrong and nobody can predict the weather this far in advance. Given that you can't just be late to your cruise, it is always a good idea to arrive at your departure point at least a day early and, in this case, Rome is hardly a hardship post.

The added benefit of an overnight is that it takes all the stress out of your connection. If you do misconnect, you will be on the next flight.