I have the Fulcrums which have been a solid wheel, no complaints. I don't know what you have on your Roubaix so its impossible to say of the Fulcrums are better. What characteristics are you looking to improve? Regardless, I would look to the newer wider profile rims. Also, you can get good deals from the likes of Merlin, Wiggle, etc. When I ordered mine, I was able to add Conti GPII 4000s for only a couple of bucks more. Way less than had I purchased the tires separately.