Well though I have zero linux experience I thought these instructions were clear enough so I’d give it a go as I really want to replace all my airport expresses so all my zones can use RAAT and be able to play together with my other Roon RAAT zones.
I bought two HiFiBerrys one with the Digi+ board for connecting to the home theater receiver via coax and one with the DAC+ board for use with active speakers in the kitchen.
Building them was easier than I thought, though the HiFiBerry acrylic cases are very cheap looking and definitely to be hidden 
I followed the instructions carefully, downloading all the programs was pretty tedious and took a while but not too difficult. Burnt the card connected to the Pi, updated everything etc. Installed Roonbridge. Great, nearly there. Check Roon is seeing the device, yes great nearly there…
But I need WiFi for these two rooms (unfortunately there is no other way.) Set up the Wifi on the Pi as instructed but Roon won’t see the device and neither will Fing find it unless they are connected to the router via ethernet cable. Argggh.
Try the second device, everything goes much quicker of course, but the same problem there as well. Arggggggggggggh
I did check the suggestion to run ifconfig see if there is anything in inet addr and there is. Here is what I get However all my other devices are on 192.168.1.X so something does not seem right with the WiFi setup.
So what do I now? Please bear in mind I have no linux skills and so I can only follow setup by step instructions.
Many thanks
