has he been exposed to any dusts or molds?
http://www.firststatevetsupply.com/store/
click disinfectant for Oxine.
info about some forms of respiratory illness:
http://www.shagbarkbantams.com/page11.htm
for now..I'd get some Tylan 50 injectable..and syringes..available at most farm/feed/livestock supply stores
(and at the first link).other meds with info available..
click antibiotics..injectables and water solubles...
always remember that chickens, especially roos, hide illness till they are very sick.
a hoarse crow is a possible early symptom of respiratory illness.
give extra protein, such as egg..keep well fed..and give vitamins..poultry vitamins..
or Poly-vi-sol liquid baby vitamins,,Enfamil brand..No IRON..give 3 drops on beak once a day for 2 days, then 2 drops for 2 days then 1 drop for 3 days.
keep warm, dry and protected from draft.