I am not ashamed of the Gospel, for it is the salvation of God for everyone who believes: first for the Jew, and then for the gentile. For in the gospel the righteousness of God is found, a righteousness by faith, from first to last, just as it is written "The righteous shall live by faith." (Romans 1:16-17)
Ok, so I wrote that out pretty well from memory. My leadership class, VLI, just had a midterm and we had to memorize this verse, and then explain what Paul was saying to the Romans.
So for fun, I'm rewriting my answer a bit for you:
Paul's letter to Romans came at a time when there was a scism between the Jewish and the Gentile believers. You see, the Jews had been ordered out of Rome by the leader of the time. Then, when they were finally allowed back in, things had changed. The church which had always been under Jewish leadership was now being helmed by gentiles. So the Jewish believers began to assert their authority over the gentiles, by virtue of being "God's chosen people," and they emphasized the things that made them different from other nations: Celebrating certain holy days, holding strict dietary restrictions, and of course circumcision.
So Paul here is pointing out that becoming more ensconced in Jewish tradition is not the way to salvation. In fact the only thing that can save you is your faith. He also reiterates that this salvation is for everyone, the Jews and the gentiles. Note that he did not say the Jews and those people who become Jewish in order to follow Christ. Nope, Jesus died for everyone, as they were. It is not necessary to change who you are in order to be saved, you must only believe in the Lord Jesus Christ as your savior. (The change happens after you take that step, believe me). But whether Jew or Gentile, Greek or Roman, slave or free, the message of Christ is for everyone. Yes, even you.