External and Internal Peace
Closely connected to Paul's letters to the Corinthian church was the letter he wrote to Rome while there in Corinth. There's not much Christian law here at all.
Paul spends most of the letter wading through a lot of theology to correct some false impressions, but it seems his ulterior motive is to promote harmony between the Jewish and Gentile Christians in Rome. He points out that Jews have not been utterly rejected, but that they do have to come to the Cross to remain in covenant with God. Meanwhile, the Jews need to fully embrace Gentiles, and they must learn to recognize that God doesn't demand from Gentiles what He once demanded from Israel. Paul invests a good bit of explanation in the doctrinal emphases of otherworldly orientation, predestination, and feudal surrender to Christ.
The first thing that sounds like covenant boundaries is in Chapter 13. This has been misread by most people since Paul wrote it. The chapter begins with a warning that God has permitted the Roman Empire to conquer a chunk of the world for reasons we may never understand. Still, it's for God to choose, and resisting Rome is resisting God. Give the Romans what they demand.
However, in the second half of the same chapter, Paul also declares there are limits. But instead of pointing out what Roman cannot demand of Christians, he emphasizes God's demands as a higher priority. Sacrificially loving your fellow believers and offering some compassion for outsiders is the real core of what God demands. Thus, if you can build your life on His love, He is satisfied with that. Obedience to Rome is not reckoned as an end in itself, but is a general commandment as a means to some other end.
Paul is careful to use language that means it applies to any other government we might find ourselves under.
Then he offers a restatement of something that featured in the Corinthian letters: peaceful coexistence with Jews who are fussy about meat. It was pretty rare to find kosher meat in a Gentile public market. Regulations might actively hinder starting up a local kosher market. Thus, it was no surprise a lot of Diaspora Jews avoided meat, because kosher was a lot easier for everything except meat. Once again, there was a bit of debate there between those who had carried around a residual sensitivity about meat and those whose faith recognized God didn't actually care. Paul was trying to establish boundaries for peace -- let people walk in their own convictions. Focus on ways to build peace. That's a matter of Covenant Law.
The rest of the letter is mostly administrative stuff. He mentions Phoebe who most likely carried this letter to Rome. She was a deaconess at the church in Cenchrea, the port city opposite Corinth on the thin isthmus where wagons carried freight between the two seas. There are lots of personal greetings from people working with Paul and to the people in Rome.