Roon objects to the idea of “Directory Views” - it’s just not how Roon wants the experience to be. There has been a lot of discussion, like here
and here
Personally I think most of what may be achievable with folders can be done with file tags and / or Tags within Roon. Also, give yourself some time with Roon - it may change the way you experience your collection. Because, also just my opinion, folder structures while once the only way to organize a file collection are a limiting factor too and will never suffice (so why not using them as less as possible).
As for “Album Artists”: have you had a look at the Knowledge Base, especially https://kb.roonlabs.com/Metadata_Model - it explains how Roon sees and treats those entities. Maybe I didn’t understand what you’re requesting but to me it seems like Roon already does differentiate here.