We are all given the opportunity to believe (this is what I believe Paul to be explaining). Through natural revelation we are given truths about God and even the Godhead, to the extent that we are guilty. Christ is not a phenomenon that stands in contrast of God's nature, but instead personifies that very nature. If we can know God then we can know God's salvation (we know that God is a God of mercy and redemption). The gospel is that this salvation has come, the Kingdom is at hand.
So my answer is that all have been given an opportunity to believe, although perhaps not the same opportunity. Those who have never heard the gospel of Jesus Christ have, not hearing the message, still rejected Christ on the grounds of God's general revelation.
I assume that you are making reference to Romans 1. What Romans 1 says is that natural revelation is enough to condemn a man, but not save him. There is only a Creator in Romans 1, not a Savior.
Secondly, this passage is a condemnation of ALL men, unless you are telling me that you are not a sinner.
Romans 1:18–32
God's Wrath on Unrighteousness
[18] For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. [19] For what can be known about God is plain to them, because God has shown it to them. [20] For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. [21] For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. [22] Claiming to be wise, they became fools, [23] and exchanged the glory of the immortal God for images resembling mortal man and birds and animals and creeping things.
[24] Therefore God gave them up in the lusts of their hearts to impurity, to the dishonoring of their bodies among themselves, [25] because they exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator, who is blessed forever! Amen.
[26] For this reason God gave them up to dishonorable passions. For their women exchanged natural relations for those that are contrary to nature; [27] and the men likewise gave up natural relations with women and were consumed with passion for one another, men committing shameless acts with men and receiving in themselves the due penalty for their error.
[28] And since they did not see fit to acknowledge God, God gave them up to a debased mind to do what ought not to be done. [29] They were filled with all manner of unrighteousness, evil, covetousness, malice. They are full of envy, murder, strife, deceit, maliciousness. They are gossips, [30] slanderers, haters of God, insolent, haughty, boastful, inventors of evil, disobedient to parents, [31] foolish, faithless, heartless, ruthless. [32] Though they know God's righteous decree that those who practice such things deserve to die, they not only do them but give approval to those who practice them. (ESV)
