First thing you need to do is sepearate your rooster from the other chickens and keep in him a warm place. Bring him inside if you can and when you do chicken chores, do the healthy bids first and minimize cross contact. Keep a close eye on him. He may have a respiratory infection.
It would be good if you could find an avian vet...even if it's just to describe the roos symptoms and get some idea of how to treat. Chickens don't get colds...so it could be something a bit more serious.
Well, an update and all positive. Took my little rooster to an avian vet (expensive but worth saving the flock) Not viral!!!! Gave me antibiotics for the roo and the rest of the flock and everyone is healthy as heck.