Putting new pads on grooved or warped rotors causes the rotors to eat up the new pads. I tried to be cheap one time and put new pads on grooved rotors and the rotors ate up the new pads in only a few months.
Sean is right, the rotors aren't supposed to be turned. They'll end up being too thin afterwards. Be prepared, it takes a bit more effort to change the rotors and they tend to be more expensive (like anything else for LR).