I've read Romans 1 a thousand times.Yes, I know. He had been doing so since the 1st chapter. Try reading Rom.1, then ask if Paul believes no one on earth has the ability to believe in God.
Rom 1:18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, 19 because what may be known of God is manifest in them, for God has shown it to them. 20 For since the creation of the world His invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse, 21 because, although they knew God, they did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened.
Show me where the word "believe" is there. It tells me that men had some knowledge that God exists, but they suppressed that knowledge and changed the glory of the incorruptible God into an image made like corruptible man—and birds and four-footed animals and creeping things. This is where all the false religions come from.