Hi Huw,
Sorry your earlier post didn’t get a response. I’ll put a notification here for @mike and @vova and they will pick this one up.
I don’t know the answer to the Sooloos library issue, but I’m confident others will.
The Tidal albums were imported during setup when users are offered pre-made collections (selected by Roon staff) by genre. Initially one of the genres was selected by default so clicking through the setup options without deselecting it imported that collection into your library. That may now have changed, I haven’t done a recent fresh install to check.
This post set out the steps you can take to batch edit the Tidal albums imported as at a particular date:
After removing albums there will be a period for Roon and Tidal to synchronise. You can hide albums while they do that and clearing the Tidal cache about a week after deletion may assist:
https://community.roonlabs.com/t/how-do-i-clear-my-tidal-cache/4010