Wanna know the central theme of Romans and why Paul wrote to them? (Right answer…we are totally going to get an A less the minus in this class…)
The primary theme running through Paul’s letter to the Romans is the revelation of God’s righteousness in His plan for salvation (faith), a/k/a the gospel. “For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. For in it the righteousness of God is revealed from faith to faith; as it is written, “But the righteous man shall live by faith.” (Romans 1:16–17).
Paul showed how human beings lack God’s righteousness because of our sin (1–3), receive God’s righteousness when God justifies us by faith (4–5), demonstrate God’s righteousness by being transformed from rebels to followers (6–8), confirm His righteousness when God saves the Jews (9–11), and apply His righteousness in practical ways throughout our lives (12–16).
At the core of Romans is Paul’s basic gospel message dealing with the misconceptions and heresies of Judaism. Paul shows that all (Judeans and gentiles alike) fall short of the glory of God, and that in order to be saved from their sin and condemnation, all are in need of a righteousness not their own. Many of the Jews even believed they possessed salvation solely on the basis of being Abraham’s descendant, a la “saved by association.” Beyond this, the Jews also thought they determined who was eligible for salvation because they owned it, i.e. they shared salvation only with those willing to become Jewish converts before the coming of Christ, and when these proselytes converted to Judaism, they had to be circumcised and willingly put themselves under the Law of Moses. With the coming of Christ, Christianity was completely rejected by many of the Jews. They didn’t believe Jesus was the Messiah, and further, they opposed the preaching of Jesus as the Messiah even to the Gentiles. The Jews who converted to Christianity wanted to acquire ownership and control just like they had done in Judaism. These Jews insisted that to be saved, Gentiles needed not only to believe in Jesus as the Messiah, but they must be circumcised and keep the Law.
To the Jews, Abraham was their father; they were his chosen sons. Paul is doing some serious correcting in Romans 4 – he not only shows the Jews that they’re mistaken concerning the righteousness of Abraham, he also shows that Abraham was justified by faith (apart from works) and that is the “father” of all who believe, Judeans and gentile alike. Abraham’s righteousness is the exact same kind of righteousness that God has made available to us on the same basis.
Abraham was justified by faith alone, apart from works (4:1-8), and he was justified by this faith as an uncircumcised gentile (4:9-17). Finally, Abraham’s resurrection faith (4:17-25) is just like that which is required today – the promises God makes are unwaveringly certain. God can “give life to the dead and call into existence the things that do not exist,” just as he did with Abraham and Sarah who were the dead ones in the sense that they could no produce life (4:19; Heb. 11:11-12), yet out of the deadness of Sarah’s womb He brought forth life. Later, when Abraham was told to kill his only son, he knew that God would bring back his dead son to life because he knew God must keep His promise (Heb. 11:17-19; cf. Gen. 22:5). Paul’s gospel teaches us that true faith is always fixed upon God’s Word (Rom. 10:17), and we must have faith…true faith in what the Word says, as Abraham certainly did.
According to Grieb, Paul wrote to the church at Rome for eight reasons– to introduce himself and his theology (especially his controversial gospel that excluded the law for Gentile converts); to correct false impressions about what he taught; to reassure the Jewish Christians of Israel’s priority and irrevocability of God’s covenant with it; to reassure the Gentile Christians of God’s impartiality and that they were included under God’s covenant promises as well; to urge Roman Christians to stop fighting over stupid stuff and live together in harmony, albeit with diversity; to recommend Phoebe as a helper and part of the important mission ahead; to start laying the foundation to build Roman house churches so they could become the base of operations he would need for his impending mission to Spain and…”above all, Paul wrote to proclaim the gospel of God to them.”
 Grieb Katherine A. The Story of Romans. Pages 14-15. Louisville: London: Westminster John Knox Press, 2002