My cousin fell through a roof and landed on his head. Chances of survival?

If he is in a coma this is the best thing for him as it will give the brain plenty of time to recover from the injury, he could be out for some time but as he is still with us now that is a good sign, depending on the severity of the injury it could mean some kind of brain damage but only time will tell what effects if any this may have. Good luck and all the best for you at this difficult time.