Roosters are always jumping down from high places and roosts. I've dealt with this many times. Lower their roosts and eliminate high places they can jump down from as best as you can. Try caging him for rest and relaxation. Most roosters dont like being caged and will go nuts in the cage because they want to be with the hens. If you can cage him in the chicken pen with his hens, that might or might not work, it just depends. If he's a wild one, he could further aggravate the injury. In any case, he needs time to heal the injury. It might take a few days, a week, a month, or never. You can add vitamin B complex to his feed, crush a few tablets into powder and sprinkle it onto his feed to eat. It may help speed up the healing process. Release him in about 5 days and see how he walks. If he's still limping, put him back in the cage for one week continuing with the vitamin B complex. Time heals these types of injuries. I dont recommend giving him aspirin to relieve pain. Aspirin only masks the injury and if he's up in the cage, he could further injure a tendon or ligament. In this instance, you want him to feel pain so he doesnt worsen the injury.