Personally I think using a rotary on carpets is complete overkill due to the weight of the machine and the risk of damage.
I used one many years ago on a commercial carpet and it took alarming amounts of fiber out of the the carpet, not far off damaging it. Goodness knows what it it would have done to a domestic carpet which it seems many companies use them for!
It is sort of beyond me why these machines are sometimes advertised as carpet cleaning machines, when in fact they are floor cleaning machines.