Hello there,

The only way I can think of to cast audio would be to either use https://oculus.com/casting or to use some sort of Bluetooth transmitter to stream the audio to the PC, and capture your voice separately and funnel it into OBS.

I'm sure you can find Youtube videos from other streamers that can do a better job of putting you in the right direction than me, but I hope it helps.

Godspeed.