Assuming you will be on Wonder, which I will be on in September? I have been reading reports from that other social media site that CC doesn't let us mention, because there isn't much information here. It appears that while the ship docks at 7:00am, many people are reporting they're not getting off until 7:30am.
So I think the chances of making the 7:44 regional train are very slim. I'm hoping to make the 7:58 train, but have also adjusted my plans in case I miss that and have to wait for next train at 8:44 (not sure why there's such a long gap), which gets into Rome at 9:30. Because of that, I have picked a Colosseum tour group that starts at 10:00 to be safe. If I'm early, so be it, but better than missing the start.