Sorry about your rooster. Has it been freezing weather there? I would check his feet for evidence of frostbite, look for green bruising or swelling of his legs, numbness or paralysis in either leg, and curled under toes. An injury jumping might have hurt his legs. While at it, look under his belly for any evidence of lice or mites. Tell us what his poop looks like as well. Isolate him in a basket or dog crate and offer him some water. If you have electrolytes or Poultry NutriDrench that would be bood as well. If he drinks, then try to get him eating some cooked egg or wet chicken feed.