Caponizing is a tricky business with a rooster. How old is the bird in question? There's an age limit for a successful outcome (meaning your bird lives through the procedure), I'm not sure right off how many months is safe. You could look on the caponizing thread in the meat bird section and see what ages are appropriate. Most vets don't do caponizing, I think your best bet would be to put a wanted ad on your local CL or similar in the farm and garden section, see if anyone local has mastered the procedure. Again, it's not so simple as castrating a mammal as the testes on a bird are internal, and the chance of a bad outcome is pretty decent, even with an experienced caponizer.
IMO, an animal can have a great life right up until they become dinner. The two aren't mutually exclusive.