Is there a way to find more complete metadata than Roon provides? As an example, the complete Sony (47 disc) recordings of Tafelmusik show only movement number and description (Adagio, Vivace, etc.) and track timing. No composer or composition titles. Neither in Album Info or Credits. Seems a pretty basic data grab. Am I missing something? Using my iPhone app at present. I’ll check later with my laptop but I suspect the same.
It’s album dependent. Some albums have excellent metadata, some not.
The best you can do is try a reidentification in case there is other metadata available.
Or resort to file tags.
For many large box sets Roon only has a stub of information, usually just the album title and the album artist. It fills in other information from your file tags. My guess is that you have incomplete file tags and Roon has (almost) nothing. If so, you can put more into the file tags, manually or by trying different metadata sources. Also, if the disks in the set correspond to previous, smaller, releases, you can have Roon identify them individually.
-SK
Just checked usual metadata sources (which Roon draws from) for that particular boxset. Allmusic.com has only the boxset name, performer, and catalog number (88875030622), but none of the discs/tracks. Same on discogs.com. Musicbrainz.org has nothing.
In general, even major labels fail to provide good metadata for their boxsets. I’ve spent way too much time entering metadata by hand (with the Mac app Metadatics) for boxsets 
When the rumoured project to leverage our entered metadata in the future, this problem will shrink considerably.
Team Roon just has to find a way of protecting us from poor user-entered metadata. Some of the screenshots of user metadata are shocking. (“I’ve always done it like that, and it suits me, even though it’s illogical and inconsistent.”) 
Thank you for the input. I shall continue to treat Roon’s classical metadata idiosyncrasies into a game of “Who wrote this and what is it?”, despite recurring nightmares of listening exams from my music conservatory days. 