Me vs. Rockset...

[ROTORYWING]

I have had good luck making an adapter to use a impact wrench to remove stubborn over rocksetted muzzle devices

 

[lwarner]

As others have pointed out Rocksett breaks down from water not heat. My method has always been the overnight in water method and it's always come off easily.

 

[DirectDrive]

Shouldn't this be done by clamping the barrel in the vice (with blocks) instead of holding onto the handguard, sending the torque through the receiver?
Not picking apart the OP's question or technique. I'm asking because I have a similar issue.

Yes.
When working on a muzzle device you should be clamping the barrel.
Not the rail.
Not the receiver.