A happy ending to the microrendu saga. I spoke with Vinnie and Jesus at Sonore over the past few days and we were able to get my issues sorted out. Here's the synopsis.
After a week or so with some help from Vinnie Rossi and the awesome tech support at Sonore, we are up and running.
I first restarted my whole home wifi network, renaming the time capsule and getting new passwords. I then set up the airport express as a wireless network extender, which required to hard reset the airport express, and confirmed that the home network is indeed working. That required the airport utility.
The next step was to hook up the microrendu to the airport express via Ethernet cable. Once I ran diagnostics on the microrendu and confirmed we had the updated firmware, we moved on to ensuring the system was booting up on the correct order. It's important (apparently) that the DAC boot up first and then the microrendu. So, once I did that, the Microrendu automatically popped up in Roon as an audio out. To be clear I am not using the Airport Express as an AirPlay device, I'm using it as a wireless network extender.
Thanks so much to Vinnie Rossi and to Jesus from Sonore for their help. Just wanted to let you know how it all turned out for the best!