Asio4All is the only solution I’m aware of for Windows. Specifically you have to configure it for device aggregation.
I’ve been waiting for people to get the AIRA units to hear how they’ve been integrating them into their rigs. The TR-8’s USB implementation offers really cool functional potential, but the fact that it’s mutually exclusive with your interface (without the Asio4All hack), combined with the 96kHz requirement (which I find baffling) are serious issues.
I’m hoping Roland do an update that works more like Virus Total Integration or the upcoming Elektron Overbridge. That would be far more practical for studio use.