Back to the OP,
Romans was written especially for Jews returning to Rome after Claudius ban (Acts 18), because the non-Jewish Christians were now the leaders and the mingling was not as easy as at first.
Well, to whom COULD Paul have written the Epistle to the Romans?
The Ancient Church understood (and understands) it to have been written to the Church at Rome.
Some may understand it to have been written to Jews only...
At which point we must determine if the Jews to whom it was written were Christians or non-Christians...
And then if non-Christians, if they were potential converts (enquirers) or sworn enemies of Christ...
Some may understand it to have been written for Gentile Christians only - I don't know anyone who thinks so...
Who else? Non-Christian gentiles?
Druids???
But if it was written to and for the Church at Rome, its message would be for Christians only, and IF the Epistle is indeed pastoral, and the ancient Church did and does consider it pastoral, then it was written to address NEEDS in the Church at Rome.
And we know that one of the needs was the conflict between two kinds of believers, the Jewish Christians who established the Faith of Christ on earth, and the Johnny-come-lately Gentile converts to the Faith, most of whom entered through Paul's efforts...
The conflict involved the perception by the founders of the Faith that Christ, being a Jew and preaching only to the Jews, intended His Faith to be the Jewish Faith, and that entry into it meant entry through the Mosaic Law of the Jews...
Paul's job was to wean the Church of Her Mother, Judaism and the Levitical Laws of the Jews, which had been a good Nanny that Christ should enter the world through the Jews, but now, after His departure, had become a hindrance, and the old toys of the childhood of the Faith, needed to be set aside, and the Faith needed to mature into adulthood...
So that the observable actions, which are the only ones enforcable by Law, which comprised the righteousness of the Jews, and were actions anyone could take on his own power and volition, were set aside in favor of the actions of Grace, against which there is no law... And the obedience to the Levitical Law was replaced by obedience to "Those having the Rule OVER YOU" in an enterprise known as putting the Old Man of Sin to death by the mortification [deadening] of one's own members in one's own flesh. A long and painful process known as taking up one's own cross AFTER an initial denial of self...
This internal self-denial is to be masked and hidden... Fasting is masked by cheerfulness and wearing nice clothes, for instance... We are to be hidden in Christ, and directed by experience elders, even young ones like Timothy... So that inward obedience to Christ replaces outward obedience to the Law of Moses... And the righteousness of the Christian thereby exceeds that of the Jew, for the inside of the cup is cleansed.
And the Jews as a People of Faith KNEW they NEEDED this, which is why they flocked to John the Baptist for REPENTANCE and Baptism... But John could only give them the Baptism of Repentance, and the Prophetic words that "One is Coming of Whom I am unworthy to even untie His sandals..." Whose Baptism John sought, and Whose Baptism John gave, that we who follow Him, should be so baptized and should therein find all righteousness fulfilled...
So the outward Faith of the Jews, their Nanny the Law, became the inward Faith of Christ, their Father...
Arsenios