I believe the way it works on most other headsets is that the device is paired with the computer. The mic on the headset then becomes a microphone you can choose in the sound section of system preferences. I think the speaker becomes an output too ... I'm not entirely sure. 😕
If that's the case, then going into Ventrilo and changing the hardware input mixer, and output device, should make it work.
But I really don't know for sure.