The apostle Paul wrote an introductory letter to the church at Rome. He had knowledge of the church but had not been there nor seemed to know anyone personal. He knew they were brothers and sisters in Christ and longed to see them. The Roman church possibly started from Jews or proselytes converted on the day of Pentecost in Acts 2. Paul wrote the letter during his ministry in Corinth towards the end of his 3rd missionary Journey before returning to Jerusalem (Acts20:2, 3 and Rom 15:25).
In Romans, Paul explains the born again experience in its entirety. He addresses no particular problem as to the occasion of the letter, but in Romans chapter 6 he addressed the Antinomian tendency of society and the carnal persuasion of mankind to neglect so great a salvation. He postulates in chapter 6:1 a plausible thought, an abomination of the doctrine of grace, "What shall we say then? Shall we continue in sin, that grace may abound?.
Paul wrote this epistle from Corinth, a Roman colony, during his 3rd missionary journey. He had first hand knowledge of Roman culture and logic and certainly was exposed to Corinthian behavior and problems. Paul wrote an airtight case against mankind's sinful nature. Chapter 1-3 is an all encompassing case against Jew, gentile, and all mankind and their need for God's righteousness "for all have come short of the glory of God." (Rom 3:23).
The latter part of chapter 3 Paul presents the sacrificial death of Jesus as a basis of Justification through faith in Christ. Now because of God's free gift salvation is available to all. We are saved from God's wrath; we are justified before God; and we are saved by grace through faith in Jesus Christ. In Chapter 4 Abraham is given as the great example of saving faith without works or the law. Paul's example strengthens the case that righteousness comes through faith alone and not by works, religious rites, or the law.