I am not an expert, but I’ll try to throw something out here… If I am wrong in any of this, please correct me!!
Paul’s epistles are generally regarded to be the earliest written works in the New Testament (closely followed by, and some scholars say even simultaniously with, the Synoptic Gospels). Even so, dating them exactly is difficult. The date range usually given today is from 50-60AD.
We know that for some years, the center of the early Church was in Jerusalem, not Rome. (How long precisely, I am not sure). There is also the fact that St. Peter did not travel directly from Jerusalem to Rome, he was with Paul at some points and also worked to set up Christian churches throughout the region (including Antioch, thought to be around 47-54AD).
This means that Paul could have written his letter to the Romans before Rome became the center of the Church. And even if Peter was in Rome, Rome is a big place, and Peter was clearly more of a leader for the Jewish Christians while Paul was clearly an apostle to the Gentiles, as is seen throughout the New Testament. Therefore, it is still logical to me to think that Paul would have reasons to write his own letter to the Romans, to evangelize and encourage “his” Christians there.
As for the canon of the Bible and when it was established, Catholic Answers has a tract of interest to you called “What’s Your Authority?”… here is a quote:
…the Catholic Church to recognize and determine the canon of the New and Old Testaments in the year 382 at the Council of Rome, under Pope Damasus I. This decision was ratified again at the councils of Hippo (393) and Carthage (397 and 419).
You can read the full tract at
catholic.com/library/What_Your_Authority.asp
I do not know personally about the Council of Trent, but in light of the Reformation and the Protestant decision to remove books out of their OT canon, it would seem to me very probable that the Church did in fact re-address the issue of Biblical canon at the Council of Trent – but only to ratify once again the same canon the Church has had since 382!!
Also, I believe this would make Trent the first Ecumenical Council to make a statement on the Biblical canon, since none of the other councils given by the Catholic Answers tract appear to be general or ecumenical councils. They appear to have been regional councils, the decisions of which were accepted by the entire Church until formally declaring it so at Trent. Remember, the general councils are historically called in response to actual heresy, or disagreement about a particular belief/practice. No one disagreed with the Church’s list of canonical books until the Reformation!! Therefore, there was no need for it to be specifically addressed until the Council of Trent.
The online version of the 1917 Catholic Encyclopedia (written before Vatican II, obviously) has a detailed article on what Church councils are, and what makes some councils ecumenical (general) councils.
newadvent.org/cathen/04423f.htm
Hope this helps, hopefully somebody else out there with more knowledge than I can explain it more clearly.
+veritas+