Stilton - please understand that whilst a 'rolling take off' can be from the ground (especially with wheeled undercarriage) the same profile can be carried out from a very low hover when there is insufficient power to either hover higher or make a normal transition.
This technique s known as a 'cushion creep' and relies on gaining translational lift shortly after losing the benefits of ground effect, at which point the aircraft will want to climb away.
The venerable Wessex at high DA had a VMin limit so a running take-off in that case would be held on the ground until that speed was reached and then lift off - all to do with TR power.
And they were great fun. Tried it once at Hollywood barracks when our friendly SLF had loaded on too much kit. Stiff bollocking from the adj of the Green Howards ensued.