The rotor bolts to the main hub that wheel bearings in it. Much cheaper that way. The bolts go in from the back, so it is hard to see them unless the wheel is off, in which case you will see the threaded end of five more bolts in the hub.
The hex driver is an Allen key in a holder that looks like a big socket. A 1/2" drive is all you will be able to get.
If the hub or rotor isn't clean at the mating surface, the rotor won't run true on the hub, but will "wobble" back and forth as if it were warped. This is run-out. The rotor sits on ledge, or flange, on the hub.
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!