Well as we know Rome is near the Tiber River so it was difficult for people to cross it to spread Christianity.
As Roman Emporer, Constantine declared Christianity to be the official religion of the Roman Empire. At the time, the Empire was vast, so Christianity spread quickly.
It wasn't so much the geography or road systems as the fact Just about everyone spoke greek
The Pax Romana (Roman Peace) did not affect the spread of Christianity. If anything it helped it because it is a term historians have coined to indicate a period of relative political stability in the Roman empire from 27 BC to 180 AD.
Christianity did not easily spread through the Roman Empire. See the related question, "How did Christianity spread throughout the Roman Empire?"
By 325ad Christianity had spread throughout the Roman Empire and to Britain. If you google "spread of Christianity map" you will find maps showing the spread.
Christianity
It spread the faith, thus proving the statement 'the blood of the martyr's is the seed of the church'.
They used force
prediction how do you think italys geography and romes location would affect the spread of romes influence
The spread of Christianity had political ramifications for the Roman Empire. The empire split into two, Constantinople to the east and Rome to the west
It could not decline from nothing - it did not exist until after much of what was to become the Roman empire was already under Roman rule. It spread, particularly after the Romans accepted Christianity under Constantine
The Romans who remained pagans did not contribute to the spread of Christianity Neither did Julian, who was the only pagan emperor in the Later Roman Empire