I agree with jjthink I'd just go for it and rescue the poor boy
forget about the whole stealing part you are NOT stealing anything you are rescuing him. After you catch him and briing him into a nice warm place then go tell the neighbors you got him out of the tree and brought him in where he can stay nice and warm. It breaks my heart to think the other birds froze to death and I wouldn't be able to sleep a wink knowing a poor lonesome rooster psycho or not is out there suffering like that
I bet if you did get him down and brought him into your home and pampered him for awhile he would be ever so greatful and probably not as vicious as he has been, heck he probably doesn't have the strength to attack anything at this point.