Always have bolas ready. They won't be for the Rock elemental, but for your tribe mate(s).

REX & TAPEJARA TEK SADDLES CAN EFFECTIVELY KILL ROCK GOLEMS UPDOOT SO BOBS AND NOT BOBS KNOW HOW TO KILL THES E DOUCHEBAGS

Don’t get them mixed up with a rock.
What will happen will not be good

If you are unsure if a rock is a disguised golem or not, a spyglass shows their name and level even when disguised. Also, when disguised, the rocks often move slightly as you get close, re settling onto the terrain.