Either go for a simpler thing like a button next to the door, or do it the hard way. Currently, I don't know of an easy way for this. Not even with SoHL.
When you make the rotating door knob a func_door_rotating with the same origin as the door, it will rotate as if the door swings open when you use it, not rotate as if you'd turn it. In that fact, you'd better attach the knob brushes to the door, making one entity of them.