The Book of Romans is the most theological of the books of the New Testament -- that is, it grapples with the "big issues" of salvation, God's judgment, the relation of Jew to Gentile, the new birth, the opposition of the Spirit of God to the sin of man.
Yet this book was written as a letter, addressed to people whom Paul had never met. It is believed that Romans was written in the late 50s, and Paul did not arrive in Rome until about 63. Although Paul was writing to the infant church at Rome, his primary interest was to resolve questions of the place of Jews and Gentiles in God's plan of salvation. This is an outworking of themes we have encountered in his preaching throughout the Book of Acts -- when he would go to the synagogues and argue from the Old Testament Scriptures that Jesus was the Messiah, and then speak to Gentiles in the market place or in homes and tell them of the one true God who had raised up a Savior for all mankind.
In Romans, Paul brings both worlds together in a work that attempts to give meaning to both groups of readers -- those of Gentile background, and those who are Jews. He shows their mutual dependency, argues against racial pride, and explains how God rules over history for the ultimate benefit of both groups. Most important, he gives a "roadmap" to history, and ties ancient Scriptures to the recent revelation of Christ. This allows his readers, of whatever racial background, to orient themselves as contributing members of the Kingdom of God.
Paul's intense religious upbringing initially caused him to abhor and persecute the new sect of the Nazarenes. After God knocked him to the ground, Paul went through a profound rethinking of Jewish tradition and theology. This was intensified after God called him to be the apostle to the Gentiles -- the very people he most despised. It was necessary for him to integrate the revelations he received directly from the Spirit with the Scriptures he had known since childhood. Romans is the fruit of these reflections, and it forms the foundation of most subsequent Christian teaching on the doctrine of salvation. Much of this book deals with the relations between Jews and Gentiles, and hence the relationships among different races.