Paul mentions the correct response to the gospel in verse 5, which he summarises as the obedience of faith. Although the gospel contains a free offer of salvation we must also remember that it includes the command to accept the offer of salvation. The gospel is not an offer like what we see in shops when a person can take or leave what is on show without any consequence. Instead, the gospel comes to us with divine authority to accept it. It is disobedience to spurn the gospel offer.
The response to the gospel is universal (the same everywhere). Yet Paul is saying more than that when he refers to the nations. In addition, he is intimating the success of the gospel because sinners will be brought into the church. And it will all be done to bring great glory to Jesus – it is for the sake of his name, and he deserves eternal glory because of what he has done.
The apostle concludes this opening section of Romans 1 by telling his readers that through the gospel they have received three blessings. The first is that they have a new Owner, which is a reminder that they have been taken into his kingdom, transferred from the kingdom of darkness. Jesus redeemed them from spiritual slavery so that they would be his. A kingdom all depends on its king.
The second blessing is that God has called them to be saints in a particular place, which indicates that believers can live for God anywhere. I suppose those in Rome might have been apprehensive about living for God in the place of pagan power, but even there, because they were set apart to God as his saints, they can live for him. As saints, they have the Holy Spirit indwelling them.
The third blessing is that there is a direct channel between them and the Father and the Son and those divine persons give continually from their permanently full storehouse. So the believers receive grace and peace continually from the Father and the Son.
Paul encourages his readers by reminding them that they are loved by God. This is the source of all the blessings they can enjoy and Paul will move on in this letter to describe what they are. And they all belong to the gospel!