True, Crab, the magnitude of the opposing forces will be equal no matter where they are positioned vertically, but it's the relative vertical positions that produce the rolling couple.
When the main and tail rotor hubs are equal in height, there'll be no roll, but when the opposing forces are split vertically, there'll be a roll in the appropriate direction which will continue until the opposing couple (the weight/vertical MR thrust couple) grows big enough to counterbalance - when the C of G has been sufficiently displaced from under the head by the roll.
You only put in enough left cyclic to counter the tail rotor drift force, which is the same no matter what vertical position the tail rotor is at. So those forces are essentially fixed, but their by-product (which varies with relative vertical position) is a roll.
The fuselage will only be level when the side forces are at that co-height point. Anywhere else, there'll be a roll angle.