Rockets Can knock out rock elementals. Just be sure to hit only the head, always the head, hit the body 1 time and the elemental will die before knock out. If you doubt me shoot it in the face and use magnifying glass.
There is a great little natural passage that you can kite the golem in to at 64.1 - 49.9. We tame all our Golem there. They can't get out but once tamed can be moved out. It offers a great firing position for your cannon.