rear rotor removal on 2006 Cadillac STS

cant seem to be able to get rear disc rotor off whats the trick to this

1 answer
there may be 2 phillips head screws thru the face of the rotor into the hub.if thats not an issue then soak the middle of the rotor where the hub comes thru with pb blaster and a little heat from a burnzamatic torch,then get out the hammer.