I have ducks, not chickens, but I would clip the feathers at the edges of the wound to about half an inch, so you can treat more easily. I would rinse with saline solution several times a day and keep the rooster in, away from flies (they will lay eggs in the wound, you may already know that).
I might start oral antibiotics, I would need to think about that... weighing the risk of systemic infection. If you can keep that wound fairly clean, though, you might not need the oral antibiotic. I would just have them handy.
I think I would consider a light covering over it just to keep dirt out, but I feel that letting some air get to the wound would be better than sealing it up.
Not a vet or vet tech or expert, but those are my thoughts based on some things I have read in Storey's Guide to Raising Ducks, and from the Duck Forum.
Not sure I am looking at the photo right, but could it be a prolapse of some sort? Just tossing that out there.