I have 'blades on the Allez for use as winter/wet-weather bike and they work pretty well.
I've fitted them on the Roubaix as well, didn't eventually use them, but having tweaked them to fit the Allez they just transferred-over without any adjustment so I'd imagine they'll work just the same.
I found the back fine but the front a bit short - go through a puddle and it dumps it in your shoes. This was easy to fix by pop-riviting a bit from a detergent bottle to the bottom end.
However they don't protect the brakes - they keep you dry but allsorts of muck and crud ends-up on the brakes, which is OK for weekend use but could involve a bit-to-regular cleaning if it were a daily-commute bike.