Let me try and answer your question. Even without drive from the engine, whilst you have rotor rpm you can still steer the helicopter wherever you want to go. Obviously where you end up is limited by the height and speed you were at when drive from the engine was lost. In the helicopter type that crashed at DreamWorld, you can fly for about a mile for every 1000' in height above ground from that point where you lost power. So that radius governs your aiming point for a forced landing. Obviously when you are close to the ground (i.e. landing) your options become very limited in where you end up should the engine stop. If you use up your rotor speed to stretch the glide to get to a suitable landing spot (eg open car park) you are going to arrive with a heavy thud at the bottom.
No doubt the engine wasn't delivering power to the rotor when the helicopter rolled over. Just look at the blades, they are still straight and intact so had very little energy left in them to dissipate when they contacted the ground. No doubt the first thing the investigators will look at is how much fuel is left remaining in the tank. Let's hope for the pilot's sake they find more than 20 minutes worth of fuel in there.
Edit: Media reporting of these things always follows the same script. The pilot is always a hero saving the stricken aircraft from certain disaster. No doubt the contribution of the pilot and everything else that happened here will come to light in the subsequent investigation. From what I've heard it will be a very straight forward investigation here.