Excellent news, your instructions to add 'smb://mycomputer/RoonBackups’ worked! In the Synology Roon Core settings this afterwards appears as \mycomputer\RoonBackups’ by the way. Yes, entered Username and Password in Add network share.
Also attaching two screenshots of Synology > Control Panel > File Services > SMB > Advanced Settings for good measure.
Many thanks for your help!
I 
Roon!
