To get on top of the rock with the Disintegration Field and Cloaking Device, go to the place where there are pointy spikes everywhere. Turn left onto the upper levels (turn left if facing the rock, right if not) then search around that little area (without leaving the pillars' area). You will see a ramp. Go up it then keep going until you see a hole. Boost over the hole and hold L
slightly. You should be on the other side. Keep going to get to an invincibility item. You will see a ramp in front of the invincibility item, Boost long enough over it and you should end up on the rock.