This is a known issue caused by Microsoft tightening security. The username and password is still guest and guest, to access Roon OS, but now you have to tell Windows that it’s OK to connect to your ROCK system as well.
Read this article on how to solve it. Start at step 6 if you have Windows 11 Pro, or step 8 if you have Windows 11 Home.
Accessing a third-party NAS with SMB in Windows 11 24H2 may fail | Microsoft…
Changes to SMB security in Windows 11 24H2 release preview may prevent access to third party NAS appliances or other devices.
