Is Squeezebox support enabled in Settings -> Setup?
Was there an error message? I use IP addresses instead of hostnames to rule out local DNS issues.
Did you check your networking settings? Using Jumbo frames/high MTU values are problematic.
I guess you’ll see this cpu load when your library is scanned and analyzed. This should be lower once this is completed.
Does Roon say that or the QNAP QTS? I have not seen a failing SSD yet and to my knowledge this is quite rare (compared to spinning disks). So I’d look for other causes first.