Paul addressed the Book of Romans to both Jews and Gentiles, even though Rome was primarily a Gentile city. Therefore, it is reasonable to conclude that most believers in the churches at Rome were Gentiles. The reason that this was important is that the Judaizers continued to infiltrate the local churches and Paul was determined to stop their false message of adding law-keeping to grace from taking root, and to demonstrate that the Gospel is for all, Jews and Gentiles.