The question gets to be if there is a keystroke that will increase and decrease the frequency (I.e.: Ctl-Up, Ctl-Down).
I have a Griffin Power Mate that I used with RemoteHams and basically you have to custom program it to the application to scroll as you turn the wheel (1 kHz), as well as when you press down (PTT), and press & turn (10khz).
As far as the headset goes, audio has to come out of the client device somewhere, either the built in speaker/mic or a headset.
i don’t have a RigPi yet, but I I’m learning...