I've had this sort of injury a couple times over the years. If you use a nice thick antibiotic ointment as a "glue" it will keep the detached comb in place while it reattaches which it will do in just a few days. "Glue" the comb to the head and then put the ointment generously over the top of the comb to make it so it doesn't shift.
A Wyandotte hen I had was getting her comb torn off on a regular basis. I finally decided to do a partial dubbing to eliminate the long "tail" coming off behind her head that presented a handy handle for the others to grab when they had a squabble with her. I was a complete novice to chickens, let alone dubbing. But dubbing really is not a big deal. I merely trimmed it with sharp scissors to conform snuggly with the back of her head, and it healed in just a couple days. She never suffered from having it torn off again in her long life.
Your roo won't bleed to death. Flour will slow the bleeding and eventually stop it.
A Wyandotte hen I had was getting her comb torn off on a regular basis. I finally decided to do a partial dubbing to eliminate the long "tail" coming off behind her head that presented a handy handle for the others to grab when they had a squabble with her. I was a complete novice to chickens, let alone dubbing. But dubbing really is not a big deal. I merely trimmed it with sharp scissors to conform snuggly with the back of her head, and it healed in just a couple days. She never suffered from having it torn off again in her long life.
Your roo won't bleed to death. Flour will slow the bleeding and eventually stop it.