2005 F150 4wheel drive rear rotor removal
 

How can I get the rear rotors off. Pounding with no luck, do I have to release the parking break somehow?

You may need to back off the parking brake shoe's. There's an access plug on the bottom portion (around 6 oclock) on the backing plate.

I have seen them rust to the axle and have had to crack them in half to get them off. But your most likely culprit is a very thick rust ridge around the inner edge of the rotor causing the e-brake shoes to hang up. Like stated above, back the e-brake shoes off and it should slide right off.... Otherwise, find a BFH and crack the rotors in half if they are actually rusted on solid.

Sometimes you find the locking ring on the studs themselves. Mine had 2 on the rear driver side.