Roosters can be prone to leg injuries, and high roosts or trying to get away from other roosters could have caused the injury. It can take 3 weeks or longer for a broken bone to heal, and a sprain just as long. Sprains are more common, and the higher up in the leg or hip, the harder to heal, at least what I have read from others on here. It would be good to put him in a wire crate or similar so that he is still a part of the flock or he may be attacked and killed by the other roosters when you bring him back after an absence. I have found that once the roosters are gone for a few days, the others treat him like he is the enemy. Let us know how he gets along or if he shows any new symptoms.