Not sure if anyone has added rotary to their Plasma but when it comes to Homing the Rotary the process is the same as a linear axis.
Install a sensor which is triggered at the required location. Maybe add a Tab to part of the rotary axis shaft for the sensor to detect.
With a Rotary the Hard limit ignores the Rotary axis signal for obvious reasons.
If you do not require an actual home position on the rotary then simply do not home the rotary axis and when you home the machine it will set the current position of the axis as the home position.
Cheers
Peter