"Paul, a servant of Jesus Christ, called to be an apostle, separated unto the gospel of God,"
"(Which he had promised afore by his prophets in the holy scriptures,)"
"Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh;"
This use of the word 'seed' and tying it to the flesh is interesting. I am used to seeing that the word 'seed' in the Bible often refers to Jesus, but emphasizing that it is a matter of the flesh prior to mentioning the resurrection puts me in the mind of the seed being sowed. Jesus did say that he was a grain of wheat (a seed) that had to fall to the ground and die to bear much fruit.
"And declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead:"
Interesting that the resurrection is how Jesus was declared to be the Son of God (with power, meaning I guess with the spirit).
"By whom we have received grace and apostleship, for obedience to the faith among all nations, for his name:"
The word 'apostle' simply means sent. Aren't all true believers, in a real way, sent from God once they are born again? Do you think all true believers could be called apostles in a certain sense? When Paul says 'we' here does he mean all true believers, or just a few? I notice a few verses later he mentions that all saints have received grace. Have all saints also received apostleship, being sent?
Another interesting thing about this verse is the use of the phrase 'all nations'. In contemporary English, all nations would mean everybody on planet earth pretty much. However, by saying that he has received grace and apostleship for the reason of obedience to the faith among all nations, it seems to me that he is calling 'all nations' only those who are obedient to the faith. To say that we are 'among' means to be a part of a group of distinct persons. I think this has implications in other parts of the Bible, where the term nations looks to the surface reader like it means everyone on the planet but is really meaning all the believers.
"Among whom are ye also the called of Jesus Christ:"
"To all that be in Rome, beloved of God, called to be saints: Grace to you and peace from God our Father, and the Lord Jesus Christ."