Addressing any doubts about the importance to humanity of a righteousness from God, revealed in the gospel (1:17), Romans 1:18-32 sees Paul begin to explain humanity’s problem.
Righteousness from God is revealed because God is angry at man’s unrighteousness.
And God’s anger at idolatry is not only right; his anger is also visible. The evil we see in the world is proof that God is angry at idolatry, and has ‘given them up’ to live a life characterised by all manner of unrighteousness.
God is rightly and visibly angry, but the gospel is the power of God for salvation. What a motivation to throw ourselves into Paul’s mission!