Christianity in Rome
After Jesus was believed to have died somewhere between 30 and 33 A.D. St. Paul and St. Peter came to Rome to attempt to convert it's inhabitants. They successfully got some Romans to join their newly found religion and over time Christianities popularity grew. In the beginning they were often persecuted because the roman people viewed them as dangerous. They absolutely refused to worship Caesar which was a huge offense to the Romans. Many started to dislike the Christians because of their refusal to worship the Roman gods so horrible rumors were started about them that included child sacrifice and cannibalism. These rumors led to even further hate, suspicion, and persecution of the Christians. Once Constantine took control of Rome he demanded complete freedom of religion which allowed the Christians to worship without worry. In 320 A.D. Roman Catholic was made the official religion of Rome. The same ruler, Theodosius I, also made the law that no cults were allowed except for that of the Christians. Once these two laws were put into effect people began tearing down the once sacred temples of the gods of old. Although all traces of the Roman polytheistic religion were destroyed, certain traditions still live on in modern day Christianity. An example of this would be the date that Christmas is celebrated on. Every year on December 25th a huge and important celebration was held by the Romans to celebrate the god Saturn and also the Winter Solstice. Because the early Christian priests were having trouble converting the Roman pagans they strategically made that same day, December 25th, the birth of Christ. The priests were trying to lead the Romans away from their "lie" and bring them to the priest's "truth". For the most part, even though the religion of the Romans is gone it's impact in history still lives on today in art, media, and religious traditions.
http://en.wikipedia.org/wiki/Religion_in_ancient_Rome
http://www.roman-empire.net/religion/religion.html
http://www.pleaseconvinceme.com/index/The_Truth_About_the_Date_and_Origin_of_Christmas