It is do-able. However, it is a workaround and a little long-winded. If you want, I’ll post instructions on how to do (should you wish to tinker). It’s how I used mine. You’ll have to use Roons DSP Procedural EQ and mixer to do the stereo split. Once done, you can group them together.
Actually, I found the original post which will save me having to write it!