Romans 5:12-14 is an interesting, but confusing passage. Paul is talking about sin and the law, and makes some confusing statements about what things were like before the Law of Moses was given.
Then, later in Romans 7:7-25, he addresses some of these same issues, and provides more clarity.
Sometime, I would like to really dive into these particular passages in real depth. Until then, I will read on and see if I find other passages that address this same issue.
Richard Venable