Final answer:
The Gospel likely written for a Gentile audience, particularly in Rome, is the Gospel of Mark. St. Paul played a key role in spreading Christianity's universal message, which resonated with the diverse social classes of the Roman Empire, despite periods of persecution.
Step-by-step explanation:
This gospel you refer to is likely the Gospel of Mark, which is traditionally believed to have been written for the Gentile audience, particularly those in Rome. As Christianity spread across Roman territories, figures like St. Paul played a vital role in communicating the message of Jesus to non-Jews, emphasizing its universal appeal.
Roman attitudes towards Jewish and Christian populations varied over time, with periods of relative tolerance punctuated by moments of conflict and persecution. Christianity's universalist ethos, treating all humans as spiritually equal, was radically different from the social hierarchies entrenched in the Roman system.