For what it's worth, I'm on the Surly bandwagon. I rode just about everything during my recent shopping and while there certainly is a difference between common road bikes and a touring/cross bike, when you are a big fella it's not THAT much. I'll go with comfort any day.
That being said, the Allez is a rockstar. I'd love to get one some day, as the things just fly, and man is that fun sometimes. I didn't really ride a Roubiax as I was worried about the carbon, but I'd imagine it's very similar, just a little more comfortable.