Romans is the first of the Epistles.
After the five Historical Books of the New Testament, the Bible continues with the Epistles. These are letters written to teach and instruct Christian doctrine. The first nine of the Epistles were written by Saint Paul, and the first is called Romans. It was written whilst Paul was in the Greek city of Corinth, around 56 AD, to the Christians in Rome, a place Paul had not yet visited. He writes to introduce himself and asks the people there to pray for him. In addition, Paul uses his letter to talk about righteousness which comes from God.
Romans 3:20-23
"Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin. But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets; even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference: for all have sinned, and come short of the glory of God"