Roon as an output channel for other sources? Ugh, but maybe

I have a Aurender X-725 DAC/Amp with just one digital input.
A USB input.
I use this amp with a pair of KEF LS50 for music while I am working.
But also the sounds from my PC I want to hear.
I wanted the best sound here.
So I connected a microRendu streamer to the USB input of the dac/amp.
Roonready and I like the combination and the sound.
But…no sound of my computer anymore.
I tried everything and came to the best (for me) solution:
Instal TuneBlade and VB-Audio Virtual Cable on your computer
Instal and activate Shairport on the microRendu.
Make the settings in TuneBlade (sends airplay signal to the Shaitport of the microRendu or other Airplay receivers).

When I want to hear music in RoonReady I switch the Audio App Switcher of the microRendu to RoonReady.

When I want to hear any sound of my computer I switch the Audio App Switcher of the microRendu to Shaireport. Shaireport is Airplay quality.