The letter (epistle) of Romans was written by Paul, the apostle, to the holy-people (Christians) living in Rome who had received holy spirit-life from God by means of the Lord Jesus Christ. These holy-people included those who were of a Judean/Israeli background and those who were of a Gentile (Greek, other-nation) background.
Paul may have written this letter in Corinth in the spring of 58 AD (refer to Acts 20:1-3) during the reign of Claudius Nero, while the Roman Empire was still in force. He expresses his longing to visit these holy-people for many years in order to help them in their believing and understanding of God's Word.
Paul explains the good-message of God which is regarding His son, the Lord Jesus Christ. He teaches the importance of believing that-which God gives us to believe. He shows how any man or any woman can receive the gift of holy spirit which God gives by His grace. He also explains regarding the blessings that all holy-people (Christians) have today, and tells us of the hope we have of the return of Christ and of our future glory together with Christ and with God.