I like
@anricat ’s idea of tour and transit.
Otherwise, how are you getting to the port? Any chance of lingering in Rome before heading to the port? Is your transport taking you all the way to the ship/ check-in area?
Do you recall when PATs begin? Lots of reports from other ports that by the later PATs, there is very little time waiting in line and your Boarding Group may be ready to be / already called - so just General Boarding.
In the US ports, they are not “turning away” early arrivals, but you are going to stand (usually outside) until your designated time. Those with earlier PATs will be allowed to enter before you.
If the ship wasn’t so far (like a mike or more) from the town of Civitavecchia, I’d say take the luggage to the port, drop it off and go into town to explore. I would rather walk around town than stand in a line for a long time.
(We did a port stop here, not a boarding. They used a shuttle to get us out of the industrial port. The return shuttle wasn’t running - after union hours. Then we took the train to/from Rome. So no idea where cruise terminal is. We actually just walked up to the ship. I don’t remember even going through any ID check from the Italians. This may have been
DCL’s first visit here).