Not the Roman Empire, per se, but a political entity that was relatively tolerant of non-official sects/cults. Whatever else you want to accuse the Romans of, you have to admit that they were pretty tolerant of a variety of religions within the Empire. Certainly much more tolerant than when Christianity became the official religion of the Empire.
To say that Christianity would have survived if it first arose in non-Roman Germania or within the Persian Empire is to ignore reality. Only under tolerant Pax Romana could Jesus' followers expect anything other than a noose.
Rome would accept any religion except the G-d of Israel. He was their enemy because He is exclusive, the only G-d. Those who worshipped Him did not bow the knee to Caesar.
To say that Christianity would have survived if it first arose in non-Roman Germania or within the Persian Empire is to ignore reality. Only under tolerant Pax Romana could Jesus' followers expect anything other than a noose.
Yeshua's followers were supposed to expect martyrdom and divine deliverance. They were not supposed to make a deal with the Empire in order to synthesize and become the first of many religions in Rome. Every story in the Torah and Tenach is full of brave men and women totally outnumbered who relied on the G-d of Israel and his messengers. You could just as well argue that Moses needed the Egyptian Empire to make the difficult journey to the land of Canaan in peace.
Of course your point of view is totally embraced in secular history and from that viewpoint it makes sense.