Hello @Dominic_Myers,
Thanks for contacting support, I’d be happy to assist here. Can you please let me know where your music folder is saved in this case? Is it saved directly on the iMac or is it saved on a NAS?
You can use these instructions to add your share in Roon over the network. If you are mounting the music from your iMac, you also have to make sure that sharing is properly set up and turn on “Windows File Sharing” for that location. This thread highlights the steps.
I hope this helps but do let me know if you have any questions!
Thanks,
Noris