The traditional view is that the Roman church was founded by both Peter and Paul. Few accept this tradition today. The story of Peter’s arrival in the second year of Claudius (A.D. 42) is found in Eusebius (H.E. 2.14.6). Peter followed Simon the Sorcerer (Acts 8) and answers his false teaching. According to Eusebius, the Gospel Peter preached at this time was so well received the Roan people demanded a written copy, which became the Gospel of Mark. That the church was founded by Peter and Paul refers to the fact they both eventually ministered in the city and were both buried there (Irenaeus, Haer. 3.1 – “while Peter and Paul were preaching at Rome, and laying the foundations of the Church…”
The consensus view is that the church was founded by believers who returned to Rome after Pentecost. Jews had contact with Rome as early as 160 B.C. According to 1 Macc 8:17-22, the Judas Maccabees sent an embassy to Rome in order to secure “establish friendship and alliance.” Pompey brought Jews captured at Jerusalem to Rome in 63 B.C. (Anitq. 14.4.5) and by the time Romans was written the Jewish population in Rome may have been as high as 50,000. Fitzmyer, Romans, 27. Kruse estimates the population of Rome in the mid to late 50s Rome at “about 400,000 made up of slaves (30%) and freed men and women (30%), and freeborn (40%).”
It is also estimated that about 10 percent of the population were Jews.” Kruse, Romans, 1. Keener comments that estimates vary “from perhaps a quarter of a million (extrapolated from water supplies) to over a million for its metropolitan area (extrapolated, in my opinion more reliably, from concrete census figures from ancient historians” (Keener, Romans [Cascade Commentary], 9). Fitzmyer also argues for at least thirteen synagogues based on inscriptional evidence (Fitzmyer, Romans, 28). In addition to these inscriptions there are thousands of funerary inscriptions in the catacombs.
Jewish Christianity would have come to Rome soon after Pentecost as Jews visiting Jerusalem in 30/33 returned home. Acts 2:10 lists Jews from the city of Rome as present in the crowd at Pentecost and Acts 6:9 mentions the Synagogue of the Freedmen. Although visitors to that synagogue could have come from anywhere, Fitzmyer suggests the members may have been descended from the Jews taken captive by Pompey (Fitzmyer, Romans, 29).
Raymond Brown points out that Christian missionaries coming from Jerusalem were more conservative with respect the Law and the connection of Christianity and Judaism in contrast to Christian missionaries from Antioch, such as Paul (Acts and Galatians support his point; see his Introduction, 562). He observes Paul is far more diplomatic with respect to the Law in Romans, as compared to Galatians. This may indicate the majority of his readers were Jews and more conservative with respect to the role of the Law for the Christian.
There is evidence of Christians in Rome as early as A.D. 49, when Claudius expelled Jews for rioting over “Chrestus,” likely a Latinized form of Christos, the Greek translation of Messiah. Luke refers to this decree in Acts 18:2-4. Soon after arriving in Corinth, Paul meets Aquila and Priscilla, Jewish tentmakers forced to leave Rome by Claudius. It is possible this expulsion of believers in A.D. 49 only effected the Jewish members of the congregation. If this is the case, then the congregation might have been founded by Jews, but is now primarily Gentile God-Fearers. If the church continued to grow, the percentage of Gentiles would have grown in this period.
After the death of Claudius the edit was canceled and Jewish believers could return to Rome, perhaps to discover the Christian congregations were far more Gentile than when they left. The Roman churches to which Paul wrote were therefore a mixture of Jewish and Gentile believers. The churches were not founded by Paul
This consensus view has been challenged because parts of the book seem addressed only to Jews, other sections to Gentiles. There are details in the book that seem to be addressed to Jewish readers, especially in Romans 1-4. On the other hand, there are indications that Gentiles are being addressed in the church. In 11:13, Paul addresses “you Gentiles.”
It is best, therefore, to understand the church as both Jew and Gentile. Paul deals with the shift in God’s program from the Jew to all the world in Romans 9-11, and with some of the difficulties that Jewish-Christian congregations face in chapter 14.
But what difference does it make in reading Romans if the churches are “more Jewish” or “more Gentile”? Does this change the way we might understand certain sections of Romans?