I’ve been finding that when I change the underlying metadata in an album to get rid of poor data these changes are not being picked on on Roon’s full scan of my library. I have to manually force a rescan on that specific album to get Roon to pick up any changes.
I’m running ROCK on an Intel NUC with my music on a QNAP NAS. I thought a full rescan should search for metadata changes?
It all depends on what the exact situation for each album is. Obviously when an album is identified, changing the file tags may make no difference, depending on which tags they are. (Composer or Track Artist would make a difference in this case, Track Title would not, although even there there would be traces in some views.)
Also to note is that when in an undignified album a track title does not equate to a known composition, Roon creates a new composition with the same name as the track title. This composition then exists in the database and will (usually) NOT change if you subsequently change the track details.
So there are two examples of why you might be seeing something more complex than you might expect.
I love the idea of an “undignified album”, Ludwig. 
In this instance I saw there was an artist (I think) called “Maria Callas v54”. The album was “dignified”…! After deleting the offending tag I forgot to rescan the album.
When I next spotted the v54 several general rescans had occurred. It was only when I did a manual rescan on just that specific album that La Divina v54 disappeared.