Or box sets represent a collection of discs also available individually. The box was later added for the convenience of the user to easily buy the whole bunch together. IMHO you’re better off importing the individual discs in such a case. If you wish to, you’re still able to put a “box set” tag on them.
As for the Roon metadata matching, it will depend on the available metadata for the “box set” and its organization (available as individual discs (also), discs of a multi-disc set or as a single disc with some hundred tracks (limited to digital distribution for obvious reasons)). If you want to force a representation that doesn’t match with the metadata available from Roon, the album(s) will most likely end up unidentified by Roon and you will only get/see the metadata that’s present in the files.
As of now, the support for box sets in Roon is more or less non-existent. No individual covers/disc titles and, as in your example, no possibility to group and label discs of a disc/box set. Roon’s support right now can only be called “good” for multi-disc albums (a.k.a. Sampler) without individual labelling needs.
See also: https://community.roonlabs.com/search?q=box%20set%20%23roon%3Afeature-requests