Rome's Conversion to Christianity/Catholicism

"Nicene Christianity becomes the state religion

Theodosius promoted Nicene Trinitarian Christianity within the Empire. On 27 February 380, he declared "Catholic Christianity" the only legitimate Imperial religion, ending state support for the traditional Roman religion.[citation needed]
[edit]Nicene Creed
In 325, Constantine I facilitated the Church's bishops to convene the Council of Nicea, which affirmed the prevailing view that Jesus, the Son, was equal to the Father, one with the Father, and of the same substance (homoousios in Greek). The council condemned the teachings of the heterodox theologian Arius: that the Son was a created being and inferior to God the Father, and that the Father and Son were of a similar substance (homoiousios in Greek—a difference of one iota) but not identical (see Nontrinitarian). Despite the council's ruling, controversy continued. By the time of Theodosius' accession, there were still several different Church factions that promoted alternative Christology." - http://en.wikipedia.org/wiki/Theodosius_I#Nicene_Christianity_becomes_the_state_religion

These were the Pope's at the time of Rome's conversion to Christianity:

37 St. Damascus, 366-384. He authorized a new Latin translation of the New Testament.
*Barbarian invasions begin in 375 and continue to 568.
38 St. Siricius, 384-399.