In our study of Paul's letter, we will look at God's righteousness and our proper response to that knowledge. This epistle (letter) was written by Paul to the Christians that were in Rome. The "church" in Rome was started without any apostle actually being in the city. People that Paul and his companions had led to Jesus and taught while they were in the Roman colonies traveled to Rome and some moved there to stay. They, in turn, followed the example of Paul and his fellow servants and spread the gospel throughout the city.
"Paul, a servant of Christ Jesus, called to be an apostle and set apart for the gospel of God -" NIV translation
Paul introduces himself first as a servant but the actual meaning is that of bondslave which is a servant for life who only does the will of his master. Then, he introduces himself as an apostle and it is interesting to note that Paul did not usually throw around fancy titles. There are many today that get caught up in a fancy name/title and lose sight of their calling but Paul always kept his focus on Jesus and God's will for his life. The final part of his introduction of himself is that he is "set apart" and this means anointed just as priests and other things were set apart for God's use in the Old Testament. This calling (anointing) was of God and not by his will or by any degree/proclamation of anyone else. Jesus simply showed up (in person) and told him that he was to be an apostle.
"the gospel he promised beforehand through his prophets in the Holy Scriptures" NIV translation
Paul (as Saul) was trained by one of the most famous teachers of the Jewish Law and he knew the scriptures very well. He is reminding the people that he is not preaching something new because all of the Scriptures pointed to the coming of Jesus Christ.