As Paul begins to wrap up his lengthy letter to the Romans, he is concerned that they display humility toward one another as well as unity overall.
If you are strong in the faith, how do you get along with those who are weak? Paul urges you to build up your neighbors and get along with them (vs. 1-2). Remember, the faith isn't all about you. It's about loving God and loving others. Even Christ did not come to be served, but to serve.
Speaking of unity, Paul is concerned that the Gentile and Jewish branches of the Church be united. The Gentiles have an important role to play in God's Kingdom, as is evident from the scriptures cited (vs. 9-12).
Finally, Paul shares some more details about his ministry to the Gentiles, including his desire to preach in territories where Christ had not yet been proclaimed (vs. 20). That is why he had not yet ventured to Rome, as the Church was already flourishing there. However, Paul feels that the time is now right, and that he will be visiting them soon after his trip to Jerusalem with a mission offering for the poor among the saints there. This picture of Gentiles assisting Jews, Paul points out, is appropriate because of the blessings that the Gentiles have realized from the Jews through Jesus Christ.