Help, my rooster was attacked by my dog!!!
Welcome to BYC. You can clean his wounds with Vetericyn, weakened Betadine, Chlorhexadrene, or spray some BluKote on them. Make sure that you can find all of his wounds by carefully examining under wings and the skin all over. As long as he has no broken bones or internal injuries he should heal in a couple of weeks, but watch for any infection. Neosporin ointment may also be applied to wounds.
I just went through the same thing when some friends were walking down my road, and my wild hen who likes to cross the road and lay eggs in our large barn every day just happened to go across as their dog was there. Mine was limping, and lost many tail and wing feathers with numerous cuts and bites. She has healed and is not limping as much after 3 weeks, and growing back feathers, but she stopped laying eggs.
As far as the dog goes, I found that temporarily using a shock collar on my dogs who had roughed up a few of my chickens, works well. He killed one, and we left the body out in the yard, and when he went over to it, he was shocked. After about 2-3 times, we never had to do it again. He always ignores the chickens, and for several years we have let 3 of our bigger flock roam our yard. All 4 of our dogs leave them completely alone, but they will kill chicks if they happen to get through the fence into the yard. Sorry for your loss.