You can use rooPlay and rooAIDJ together with rooNuimo, absolutely fine with the Pi4 
I also do and run ADI-2/4 for Phono (RIAA in digital) and at the same time as 4-channel DAC all with a rooExtend-Box (Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC | Page 36 | Audio Science Review (ASR) Forum).
But the ADC E1DA Cosmos is an excellent choice too 
Please keep in mind that this is the thread for the rooExtend-Box.
For all questions not related to the rooExtend-Box please use this thred:
rooExtend – The easy start with Roon Extensions - Audio Gear Talk - Roon Labs Community
Best DrCWO