The more mature in faith need to help the weaker, more immature, or less shaped by the Word.
Jesus has done this for us.
Receive each other as Jesus received you.
Jesus came to save the Gentiles, too.
Paul know the Romans Christians can minister to themselves, but he wrote boldly about Christ's grace, since he was given this ministry to Gentiles.
I'm on the way to Jerusalem with financial aid for the Christians in Jerusalem. But then I plan to go to Spain, and would like to stop by and see you a while.
Pray that I survive the Judean hostility.
How this is about Jesus
Paul didn't keep the good news just for the Jews. All the world is to know it and be invited to faith in Christ.
Paul must have heard of, or anticipated, tension between Jews and Gentiles. His wording seems carefully crafted to apply to both sides equally. On secondary issues, it's important to negotiate in this way. Many reject such diplomacy and negotiation in the Christian life, since they reject the very category of secondary or doubtful or minor issues. Since the Bible addresses everything, they think, there is nothing it doesn't give a definitive stance on. This is not true, and Romans 14-15 proves it.