Answer:
In 313 CE, Emperor Constantine issued the Edict of Milan (granted Christianity and many other religions legal status).
In 380 CE, Emperor Theodosius issued the Edict of Thessoloncia, making Christianity the official religion of the Roman Empire.
Before this, the relationship between the two crumbled especially after Emperor Nero killed a vast amount of Christians, but because of the Roman Empire, Christianity was spread a lot easier.
I hope this helps, if you need anything else just ask.
Step-by-step explanation: