Thanks for the info regarding the seat post. It's something that I'll keep in mind if I decide to go forward with the Roubaix. My current bike, a TCR Advanced, is very stiff too and I really don't mind it. I like the idea of a more relaxed geometry and hence why I'm looking to get an endurance bike. I'll also set up an appointment to take the Roubaix for a ride before making a purchase.
I really appreciate all the feedback in this thread!