There is no question that there were “bishops” in Rome, likely beginning in the late second or early third centuries. But these were not “bishops” as we would understand them today.
Roger Collins, in his work “Keepers of the Keys of Heaven: A History of the Papacy”, New York, NY: Basic Books, a Member of the Perseus Books Group, ©2009) wrote:
Not everyone is convinced that what has been called a monarchic bishop, with unquestioned authority over all of the Christian clergy in the city, was to be found in Rome even as early as [155-166], and Fabian (236-250) has been proposed as the first bishop of Rome in the full sense. It is probably not necessary to take so extreme a view. The idea that in principle there should be a single bishop at the head of the whole Christian community of the city existed well before his time. On the other hand, even after 250 the authority of the bishop over all of the Christians in the city could not easily be enforced, as it was impossible to impose uniformity in so large a city when the Christians remained legally proscribed and danger of prosecution by the state (pg 14, emphasis added).
In fact, there were disputes – “street fighting among their followers” – for control long after the 250 date. Collins recounts, “because of the house-church system, such rival bishops could co-exist for as long as they had the backing of some of the city’s many Christian groups. But the divisions usually resulted in violent clashes between the partisans of the two claimants, and in all cases the imperial government intervened to end the bloodshed and to send one or both of the rivals into exile, as happened in 235, and would do so again in 306/7 and 308” (Collins 25-26).
After the conversion of Constantine and the legalization of Christianity in Rome, the bishops of Rome found that they had wealth and splendor, and began building monuments to themselves:
They [bishops of Rome] set about [creating a Christian Rome] by building churches, converting the modest tituli (community church centres) into something grander, and creating new and more public foundations, though to begin with nothing that rivaled the great basilicas at the Lateran and St. Peter’s. Over the next hundred years their churches advanced into the city – Pope Mark’s (336) San Marco within a stone’s throw of the Capitol, Pope Liberius’ massive basilica on the Esquiline (now Santa Maria Maggiore), Pope Damasus’ Santa Anastasia at the foot of the Palatine, Pope Julius’ foundation on the site of the present Santa Maria in Trastevere, Santa Pudenziana near the Baths of Diocletian under Pope Anastasius (399-401), Santa Sabina among the patrician villas on the Aventine under Pope Celestine (422-32).
These churches were a mark of the upbeat confidence of post-Constantinian Christianity in Rome. The popes were potentates, and began to behave like it. Damasus perfectly embodied this growing grandeur. An urbane career cleric like his predecessor Liberius, at home in the wealthy salons of the city, he was also a ruthless power-broker, and he did not he did not hesitate to mobilize both the city police and [a hired mob of gravediggers with pickaxes] to back up his rule…(Eamon Duffy, “Saints and Sinners, A History of the Popes, New Haven and London, Yale Nota Bene, Yale University Press ©1997 and 2001, pgs 37-38). (Eamon Duffy, “Saints and Sinners: A History of the Popes”, New Haven and London, Yale Nota Bene, Yale University Press ©1997 and 2001, pgs 37-38).
But the only changes weren’t architectural changes. During the fourth century, these bishops of Rome sought to put their own doctrinal marks on the church.
Since the mid third century there had been a growing assimilation of Christian and secular culture. It is already in evidence long before Constantine with the art of the Christian burial sites round the city, the catacombs. With the imperial adoption of Christianity, this process accelerated. In Damasus’ Rome, wealthy Christians gave each other gifts in which Christian symbols went alongside images of Venus, nereids and sea-monsters, and representations of pagan-style wedding-processions.
This Romanisation of the Church was not all a matter of worldiness, however. The bishops of the imperial capital had to confront the Roman character of their city and their see. They set about finding a religious dimension to that Romanitias which would have profound implications for the nature of the papacy. Pope Damasus in particular took this task to heart. He set himself to interpret Rome’s past in the light not of paganism, but of Christianity. He would Latinise the Church, and Christianise Latin. He appointed as his secretary the greatest Latin scholar of the day, the Dalmatian presbyter Jerome, and commissioned him to turn the crude dog-Latin of the Bible versions [currently] used in the church into something more urbane and polished. Jerome’s work was never completed, but the Vulgate Bible, as it came to be called, rendered the scriptures of ancient Israel and the early Church into an idiom which Romans could recognize as their own. The covenant legislation of the ancient tribes was now cast in the language of the Roman law-courts [emphasis added], and Jerome’s version of the promises to Peter used familiar Roman legal words for binding and loosing — ligare and solver — which underlined the legal character of the Pope’s unique claims (Duffy, 38-39).
It should be noted that this “Latinization” was one of the things that the Reformation worked to undo. It was the focus of the motto, “ad fontes” [“To the sources”].
As Alister McGrath has noted in his “Introduction to Christian Theology,” “the Vulgate translation of several major New Testament texts could not be justified.” Nevertheless, he said, “a number of medieval church practices and beliefs were based upon these texts.”
So in addition to some of the forgeries and works of fiction upon which the papacy aggrandized itself, Roman doctrines themselves were founded upon or expanded with translation errors.