Thanks for your replies. The more I think about this and shop, the more I think it's not a good idea to get stuck with any particular number, just as you are suggesting.

One thing that makes this even more difficult is that even if I scour all the bike shops (or seemingly all of them) within a 25 mile radius of my home, I may not find the bike in the frame size I'm looking for. So, is it safe to say that if the 52 Roubaix is too small, and the 56 is too big, then the 54 would be right for me with some small adjustments? I don't understand how people can find a bike with a perfect fit unless (1) they search all over creation for a bike with that frame size and ride it, (2) get lucky, or (3) buy a custom-built bike.

Maybe I am over-analyzing this too much....