What duty did Paul say the Gentiles owed the Jews in Romans 15?

Les teaches that in Romans 15, Paul explains that the Gentiles were debtors to the Jews. Because the Gentiles had been made partakers of Israel's spiritual things, their duty was to minister to the Jews in carnal or material things. Paul was going to Jerusalem to minister to the saints, not to preach, but to bring financial help. The churches of Macedonia and Achaia made a contribution for the poor saints at Jerusalem. Les points out that at that time there were no mission boards or foreign missionaries to support, and the local church didn't have many expenses, but their responsibility was these poor believers in Jerusalem. Israel had not yet been totally set aside; the Temple was still operating, and these Jewish believers were destitute, with no welfare system, and the Temple priesthood would not care for them because they had embraced Jesus of Nazareth. Their only hope was the collection from Gentile believers. Les also notes Macedonia is northern Greece and Achaia southern Greece, and these believers were poor themselves.