I see in the thread that you have solved this, and I am just seeing this thread. I wondered if you have ever considered mapping your music folder as a network drive, and then just setting Roon to look in that drive letter instead of the whole network path.
In my case Roon runs on an always-on Windows PC and I just created a mapped drive letter for each of the folders I created on my 218+. In my case “I” is my music folder so Roon is just told to monitor that drive letter and works as expected.
I was asked the first time I tried to map to the Synology for a username and password for the NAS which validated my computer as an authorized user of the NAS and now I never get asked again.
Just wondering if this would have been an option.