In Romans, Paul says that the Gospel reveals God’s righteousness. Then he says God’s wrath is revealed from heaven. I think these are one and the same revelation in the Gospel. Thus:
For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. For in it the righteousness of God is revealed from faith for faith, as it is written, “The righteous shall live by faith.” For [in it] the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth.
Romans 1:16-18 ESV
Obviously, the bracketed words aren’t there, but I think the implication is entirely plausible. What Paul goes on (1:18ff) to describe God doing in response to idolatry in history is NOT God’s wrath. God does respond to sin by giving people over to more sin and this is “the due penalty” (v. 27), but this is not an expression of God’s wrath, but a continual and compounding provocation of God’s wrath. Romans 1:18ff does not describe God’s wrath but it describes why God is wrathful.
But the fact that God doesn’t respond in immediate wrath is because the same process is due to God’s kindness.
Do you suppose, O man—you who judge those who practice such things and yet do them yourself—that you will escape the judgment of God? Or do you presume on the riches of his kindness and forbearance and patience, not knowing that God’s kindness is meant to lead you to repentance? But because of your hard and impenitent heart you are storing up wrath for yourself on the day of wrath when God’s righteous judgment will be revealed.
Romans 2:3–5 ESV
So God’s own righteousness might be questioned because, rather than express his wrath on sin, he left it unpunished. This is exactly the problem that Paul says God solved by the cross of Jesus Christ:
For there is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.
Romans 3:22b–26 ESV
God’s righteousness is revealed in the cross which propitiates, and thus also reveals, the wrath of God (3:21-25). This was done through Israel’s participation in the worldwide sin and unbelief described in Romans 1:18ff so that their unrighteousness and unfaithfulness in rejecting Jesus demonstrated God’s righteousness and faithfulness in dealing with sin (Romans 3:1-8).
In all of this, we must not forget the mention of “your hard and impenitent heart” (2:5). Because, when Paul brings up Pharaoh and the hardening of Israel, (Romans 9:14-18), he is revisiting ground he has already covered in 1:18-3:26. He is saying that God had the right and a reason to use their sin because he had promised to bring salvation to the world. His hardening of Israel (9:18), giving them over to sin (1:24, 26, 28), was both just and aimed at being faithful to his promise to deal with sin.
For just as you were at one time disobedient to God but now have received mercy because of their disobedience, so they too have now been disobedient in order that by the mercy shown to you they also may now receive mercy. For God has consigned all to disobedience, that he may have mercy on all. Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how inscrutable his ways!
Romans 11:30–33 ESV