Romans 1
13 Now I do not want you to be unaware, brethren, that I often planned to come to you (but was hindered until now), that I might have some fruit among you also, just as among the other Gentiles. 14 I am a debtor both to Greeks and to barbarians, both to wise and to unwise. 15 So, as much as is in me, I am ready to preach the gospel to you who are in Rome also.

From the Message:
13-15 Please don’t misinterpret my failure to visit you, friends. You have no idea how many times I’ve made plans for Rome. I’ve been determined to get some personal enjoyment out of God’s work among you, as I have in so many other non-Jewish towns and communities. But something has always come up and prevented it. Everyone I meet—it matters little whether they’re mannered or rude, smart or simple—deepens my sense of interdependence and obligation. And that’s why I can’t wait to get to you in Rome, preaching this wonderful good news of God.

It seems Paul has tried to visit the Romans previously and was stopped. He does not specify if it was circumstantial or if the Lord had told him no. It is also important to know that he is on the way and ready to preach the Word.