This verse has nothing to do with the gospel. The only thing revealed by nature is the power and Godhead.
People go to hell for sin. Sin is violation of the light given you whether in creation or by conscience.
If failure to hear the gospel allows people to go to heaven and miss hell then PLEASE keep the gospel a secret!
Here is the context:
Rom 1:16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
17 For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;
19 Because that which may be known of God is manifest in them; for God hath shewed [it] unto them.
20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, [even] his eternal power and Godhead; so that they are without excuse:
Paul says he is not ashamed of the gospel of Jesus Christ. He says belief in that gospel is the power of salvation. And salvation saves from the wrath of God which is against those who "hold the truth in unrighteousness." This means they know what is right and do wrong. And how do they know the truth? Because God has revealed truth about his eternal power and Godhead by what he has created. It says that no one has an excuse for not believing.
Rom 2:14 For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves:
15 Which shew
the work of the law written in their hearts, their conscience also bearing witness, and [their] thoughts the mean while accusing or else excusing one another

16 In the day when God shall judge the secrets of men by Jesus Christ according to my
gospel.
Paul makes the case that God has written his law on our hearts so that we know the truth... in that way, no one on earth can make the excuse "I didn't know that was sin."
Failure to hear the gospel will not save anyone. The Bible is perfectly clear - there is only 1 way - faith (believing) in Jesus Christ.