I'm living in a small town in Indiana this summer and there really aren't many bike shops around, let alone ones that stock the Diverge. I found a lightly used 54cm from a great seller at an outstanding price. I'm 5'10 and wear a 32" inseam. Is this too small or will it be ok (maybe with a different stem)?

I'm 6'2" with a 33"(ish) inseam, and I just got a 58cm Diverge. I'd think you would probably need the 56cm. Can you give it a test ride? Is there a Specialized dealer anywhere near you? The Roubaix and Secteur are identical geometry, so you would be able to tell by riding one of them.

As Antipathy stated, you need a 56cm OP.

Try it out. Seems likely that it would work for you.

The Diverge is a sweet bike. I am little over 5' 6" with an inseam of 30". I found the 54" Diverge to be a good fit for me. I suspect that with an inseam of 32" a 54" frame might be a little too small for you. Mind you, if the price is really, really low you could try it out with a raised seat and see how it works for you. Without riding it yourself and seeing how it feels, you'll never know. Let us know what you decide.

Thanks for your replies. I found a store about an hour away that had it in 54 and 56. The 54 was definitely too small. It was a long way down to the bar from where I needed the seat and there was a significant amount of toe overlap as well. Really bummed out since I had to pass on a Smartweld with few hundred miles for $1400.