To knock out a Rock Elemental you can use a Paracer with a plattform sattle equipped. You now could place a ballista turret, a catapult turret or rocket turret on it. However the cannon is the absolute most effective cause it does the most torpor per shot. Not like the catapult with only 5. You also can use a Rocket Launcher wich is also pretty good.
For some reason, after the latest update, X-rock elementals (haven't checked other variants) are no longer tameable. Whenever you knock them out, they don't eat and don't have a taming bar. Forcetame also doesn't affect them, so I believe it's a glitch
To tame these turret soakers I’d recommend getting four metal gates 5 pillars 3 ceilings and 3 walls. For the trap and the pillars are supposed to prevent the golems rocks from hitting the cannon. AIM FOR THE HEAD