For nearly 300 years, from the time of Emperor Nero in the first century AD until the time of Emperor Constantine in the fourth century AD, Christians were persecuted and executed by the Roman authorities. The Romans viewed Christianity as a dangerous and subversive religion, and they were afraid of the way that it was gaining popularity among the people.
In 313 AD, Emperor Constantine issued the Edict of Milan, which granted freedom of worship to all religions in the Roman Empire, including Christianity. This was a major turning point in the history of Christianity, as it allowed the religion to come out of hiding and begin to spread more openly.
However, even after the Edict of Milan, Christians still faced persecution from time to time. The Roman Empire was a violent and chaotic place, and Christians were often seen as a scapegoat for the empire's problems.
It was not until the reign of Emperor Theodosius I in the late fourth century AD that Christianity was finally established as the official religion of the Roman Empire. This brought an end to the persecution of Christians, and it also allowed the church to begin to play a more active role in the political and cultural life of the empire.
So, while the Roman Empire did eventually embrace Christianity, it did not play a positive role in the preservation of the religion. In fact, it was the persecution that the Romans inflicted on Christians that helped to strengthen their faith and to spread their message to the world.