They don't call Paul the apostle to the Gentiles for nothing (11:13). Paul is a Jew, but he really digs the Gentiles. That's probably because they've been making his job so easy. While many Jews are less than thrilled about Jesus, the Gentiles are surprisingly into him.
Paul takes this and runs with it… around half the Roman Empire.
It makes sense that Paul would work well with Gentiles. After all, he grew up outside of the Jewish homeland in Jerusalem. He was just a kid in the Diaspora. And though he had a Jewish education, he was also exposed to the Greco-Roman way of life and would have had contact with non-Jews throughout his life (source).
So when Paul sees that the Jews aren't exactly welcoming Jesus with open arms, he comes up with other plans. Paul believes that, while God originally planned to bring salvation to the Jewish people through Jesus, now he's gotten tired of waiting and has moved on. Sorry, folks. You've gotta get up pretty early in the morning to catch the salvation train.
It doesn't matter to Paul that the Gentiles don't follow Jewish law and teachings. "Gentiles," he says, "who did not strive for righteous, have attained it" (9:30). Well, go them. For Paul, this means that there is only one divine law and that everyone instinctively knows it (2:14). The Jewish people have it written down in books, but the Gentiles have it written on their hearts. God's good like that.
Really, Paul says, God is the God of everyone (3:29). He wants the Gentiles to be saved just as much as the Jews, and if he has to bypass his chosen people to get there, so be it.
But does that mean that Paul has only praise and sunshiney smiles for the Gentile-Christians? No way.
The situation in the Roman church was actually sort of a unique breeding ground for discord between Gentile-Christians and Jewish-Christians. It all started when, in 49 CE, the Emperor Claudius threw all the Jews out of Rome. According to ancient sources this was because "the Jews constantly made disturbances at the instigation of Christus" (source, 1084) Oh, they probably mean Christ. As in Jesus Christ. Oops.
So all the Jews get chucked out and aren't able to come back until the emperor dies in 54 CE. For five years, the Gentile-Christians are running the show in the Roman church. But when the Jews return home, things get tense. All of the sudden, two different groups of Christians with two different backgrounds are coming together and trying to live in harmony. It's not easy.
That's where Paul comes in. He settles some scores when it comes to circumcision and following kosher laws. Basically, he wants everyone to just stop freaking out over this stuff (14:1-23). And even though he calls those who don't keep kosher laws "we who are strong" (15:1), he stresses that the "weak in faith" (14:1) are not any less awesome in God's eyes. No. Clearly not.
That's right. The Gentile-Christians shouldn't get too full of themselves. Paul is clear that even though the Jews have fallen short, that doesn't mean the Gentiles are better than them. He also warns the Gentiles not to brag about their superior position in God's family (11:17-18). They didn't get this post because they've done anything special; it's just because God is so generous and amazing and an all-around great deity.
Why Can't We All Just Get Along?
Basically, Paul's big goal in Romans (and in all his letters, really) is to help all Christians live in peace and harmony. Kumbaya.
For Paul, that's part of what the collection that he's bringing to Jerusalem represents (15:26). Here he has money that he's gathered from Gentile churches around the Empire. Now he's bringing it to support a majority Jewish church in Jerusalem because "the Gentiles have come to share in [the Jews] spiritual blessing, they ought also to be of service to them in material things" (15:27).
Paul knows that the Gentile-Christians and Jewish-Christians need to learn to live together if these Jesus thing is ever going to take off. In the end, he gives his life trying to bring the two sides together.
That is one dedicated guy.