I would say a resounding YES! as long as it hasnt gone mouldy I prefer (because I think the carp prefer)a lot of my cereal and particle type baits to be fermenting.The process is caused by the enzymes breaking down the bait (both protein and cabohydrates)and releasing the sugars that carp,tench and in some cases bream find so attractive.A lot of the bait buffs will be able to tell you all about the breakdown process and the fact that the process makes the protein more available to the fish etc etc but all I know is that they certainly like it once its fermented a bit!
Would definately go along with Terry D about roach though.