You mean you think there were no Jews in Rome? There had been a large colony there for several generations.
What difference does that make? Peter stayed in Jerusalem. No where in scripture does Peter teach in Rome, write to the Romans or spend time in Rome. Even Paul went to Jerusalem to see Peter, not to Rome.
Galatians 1:18 Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days.
When Paul writes to the Romans and mentions several names there no mention is made of Peter.