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.
Rock Elemental
The Rock Elemental is a massive rock monster that is typically found disguised as a stone formation. When a survivor enters its territory, it will begin thrashing and throwing large boulders. Once tamed, it can be a highly effective siege weapon to bring into battle.
How ARK players tame and knock out the Rock Elemental: what to feed it, what to knock it out with, and how to keep it safe.