From Specialized website "The Roubaix Pro features a proprietary FACT carbon crank and bottom bracket system that, because it was designed as an integrated part of the Roubaix chassis, cuts weight (an amazing 148 grams) while boosting pedaling efficiency." So it sounds like the GXP (which is for threaded BB's) will not work.
BTW: I just bought an SRAM Apex kit for my Trek OCLV 110. I don't need high-end components either