I agree that this could possibly be Mareks disease, but it is neurological for sure. It may not be something that you can identify, unless you get testing or a necropsy if he dies. Roosters can get injured because of their activity. He has symptoms of wry neck, and that and other strange symptoms can be caused by Mareks. Hopefully, itis not that, but I would continue the vitamin E dosage that @Wyorp Rock recommended.