This is the sort of warship that was the backbone of the Roman fleet in the time of Julius Caeser. It would also have made up the fleets that engaged each other when Octavius Caeser went after Anthony and Cleopatra.
The ship's motive power during battle would come from the oars - the sails would be too vulnerable to battle damage and the ram would be used to cripple the opposing ship, not necessarily to knock a hole in the hull, but to rip off the oars. Even if they were not broken, the effect on the rowers would be catastrophic. The rowers would be slaves, while the rest of the crew would be free men and the soldiers manning the upper battle deck and the castle would be Roman Legionaires.