Romans 5:18 "So then as through one transgression there resulted condemnation to all men, even so through one act of righteousness there resulted justification of life to all men."

"All means all, and that's all all means" is a favorite saying of those who oppose Calvinism or Reformed Theology.  It is used because they claim Calvinists redefine the meaning of all in verses like 2 Timothy 2:4.  If their statement is true, then consistency demands you to be a universalist (everyone will be saved).

It's clear that the "all" in Romans 5:18 can't be referring to "every single person" or else it would contradict so much of the Bible which speaks about hell and condemnation.  Instead it is much more logical to see that "all" in Romans 5:18 means both Jew and Gentile.  Jesus Christ is the single mediator for "all" men (1 Timothy 2:5), no matter race, social standing, age, sex, heritage, etc.  All have been cursed by the sin of Adam, and all will be saved by Jesus Christ.  Everyone must be saved through Christ; sadly, not everyone will.

For more examples of "all" used in context see this article.