I have run a clean instance of Roon Server on the set of tracks. I am getting the following:
2946 of 3526 albums identified. This corresponds to 83.5%, which is not bad. I could now try to manually identify the obvious albums in Roon, that could deliver a few more.
Its worth noting that usually Roon should easily identify the albums that Songkong has matched to MusicBrainz because it can understand the MusicBrainz Ids added by SongKong, it may also match a few MusicBrainz albums that SongKong did not because of differences in their matching algorithms.
It may or may not identify the albums that have been only matched to Discogs because Roon does not use Discogs, so if we assume these albums are not in MusicBrainz then Roon cannot match them unless they are also in AllMusic. However even if it cannot match the album, it is likely that it can identify the artists and performers added by SongKong so the situation is much better than if SongKong had not matched them.
I had a look at some of the albums that could not be matched by SongKong and the albums simply are not in either database