Read first about the early Church Fathers - those who suffered under the persecutions and then those who became the first Church leaders after Christianity was made State religion of Rome by Constantine.
Aren't you just a little misguided? Constantine never had jurisdiction over Rome. Constantinople is in modern day Turkey. Rome is in modern day Italy. In Biblical times, it might take a couple of weeks with a dedicated charter to make the journey. More if you were taken on board a passenger ship.
You might want to read up on Paul's journeys for familiarity with the territory in Biblical times.