As far as I know, the rotors will be the same, and the internals of the callipers should be the same. There may be an external difference between front and rear to allow different mount for front and rear, but most are the same at each end. Cable lengths will be different.
Just make sure that the rotation direction if rotor and calliper is correct for each brake.
I assume you are putting a disc in each rear wheel? It should also be possible to buy individual units, which means you could get three idnetical units, and then have no worries at all!
Steve G
Beijing