The Evolution of Religion in the Ancient World

For them the Roman religion is just what you are if you're a Roman. But it's not something you would voluntarily say, oh I fancy worshipping Roman gods now. If you were a ghoul you just wouldn't do that unless there was some kind of military action against you. So conversion is and even then they wouldn't see it as a religious conversion,. They would just see it as mixing their gods like hyphenating their gods with the Roman ones. There were however things within Rome, the Roman world that you did sort of convert to - this is what Christianity comes out of. These are the Roman mystery cults which include things like the cult of Mithras or Sol Inv