Romans 1:1-7

"Paul, a servant of Christ Jesus, called to be an apostle and set apart for the gospel of God - the gospel he promised beforehand through his prophets in the Holy Scriptures regarding his Son, who as to his human nature was a descendant of David, and who through the Spirit of holiness was declared with power to be the Son of God by his resurrection from the dead: Jesus Christ our Lord.

Through him and for his name's sake, we received grace and apostleship to call people from among all the Gentiles to the obedience that comes from faith. And you also are among those who are called to belong to Jesus Christ.

To all in Rome who are loved by God and called to be saints:

Grace and peace to you from God our Father and from the Lord Jesus Christ."

Paul

a Bond servant of Christ

v.1 Paul was a servant voluntarily out of love, not forced to follow his Lord. He called himself an apostle putting him on the same level as the 12 apostles and claims authority from God for His work.
v.3 Lineage was very important to the Jews (his primary audience) humanly, Jesus was a descendant of David therefore fulfilling God's promise to David to give him a dynasty that will last forever (2 Sam. 7:8-17)
v.5 The primary purpose of the apostles' work was to persuade people to obey God's command to follow Christ.
v.7 To all who are in Rome, called to be saints. We are not in Rome, but this letter was written for our sake aw well, we who were called by God to be His followers.