Roll pins? Rotor is held on by the lug bolts and a 6mm allen flathead screw (or two?).
You must remove the caliper -- two bolts in the back -- and hang it out of the way. You may be able to remove the floating side of the caliper, I'll check on the CD and see. Normal procedure is to remove the caliper as far as I know.
Rotor may be stuck, the rears usually are, terribly!
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!