ronks said
The epistle of Paul to the Romans has got me wondering. The church was to some extent established there at the time he wrote but I have seen little on how that came to be, prior to the Neronian persecutions.
There is a brief overview in Geoffrey Barraclough’s “The Medieval Papacy”, but I would be interested to know if more detail is available. Thanks!
  

Unfortunately we have more questions than answers.  We can draw some conclusions however.  There was definitely a pre-Pauline ministry to the gentiles although Paul assumed that he was their divinely ordained apostle.  These early communities were mixed between Jews and gentiles.   One of the qualities of all capitals is that they attract large numbers of ex-pats.  That would have been just as true of Rome as it is of Wash DC.   We know there was a Jewish presence in Rome so there was doubtless communication with the home country.  At some point early on Jewish converts traveled to Rome.  Or one can even imagine a pagan convert traveling closer to Jerusalem who then went back home to Rome.