rocker arm adjustment 4 of 12 rocker arms are loose and have a lot of play in them

after replacing my head gaskets both sides. I am putting my engine back together. 4 of 12 rocker arms are loose and have a lot of play in them. I have checked to make sure the push rods are in there right place and without turning the engine over they are still loose. I have looked this problem up and found only one answer. so far they are saying that each cylinder has to be adjusted at TDC. not sure if this is correct or not. if it is then can I use the key to turn the engine over or does it have to be manually