To whom was the epistle to the Romans written?
This again may seem like an obvious answer, given the title of the book, and the introduction from Paul in Romans 1:7:
To all those in Rome who are loved by God and called to be saints:But what do we really know about the Roman church? The book's content tells us a lot about them.
Grace to you and peace from God our Father and the Lord Jesus Christ.
First, we know that Rome was a church that had started and thrived without having been planted by an apostle. Paul, after his arrest in Acts 21, will eventually be sent to Rome as a prisoner and will bring the gospel to many people in the capital city. But up until this time, they have had to make due with second-level teachers and leaders. This explains why Romans sometimes reads like "Intro to Christianity", laying out the basics of the faith. The Romans had never heard real doctrine before!
Second, we know that the Roman church contained both Jews and Gentiles (Gentiles - for those who may have forgotten - means "any non-Jew"). This created a good deal of tension in the church, because Jews observed the whole Mosaic law in addition to Christianity while Gentiles just wanted to follow the teachings of Jesus. This pattern will be played out again and again in the early church, as Jewish Christians want to make Gentiles more Jewish, while Gentile Christians want to make Jews act more like Gentiles. But this explains why Paul will spend a good deal of this book laying out the differences and similarities between Jew and Gentile.
Third, we know that Paul had high hopes for Rome. If the capital of the Roman Empire were to become Christian, it greatly increased the possibility the gospel would eventually reach the whole Roman world. At this time in history, the Empire reached from Spain in the East to India in the West, from Britain in the North to Africa in the South. It was the greatest empire that had ever existed, and offered a chance to communicate the gospel in a common language to the whole known world.