You might want to give SongKong software a try for cleaning up your metadata. It works well with Roon, and if you search these forums you might find one of the discount offers the developer frequently offers here. I find it very useful.
I’ve been trying out dBPowerAmp, and so far it seems worthwhile – thanks. Not perfect in its handling of box sets, but far better than iTunes or Roon, and its errors are much easier to fix.
I still wish I could find a simpler workflow for adding music to my library, but this does seem at least workable.