For Album Interpret / Album Artist or what roon may consider to be “Primary Artists” / “Main Performers” you should have a good starting point with the Artist Browser.
What roon lacks are ways to expose data for browsing in more detail, as you’ve found out. 
Currently, it seems impossible to browse by conductor / ensemble / performer role - something that SHOULD be available at least within “Focus”. While roon “knows” quite alot about credits and has a detailed model for this (see here) it seems it doesn’t do much with it except showing a credits tab in the album view. 
There have been (quite) similar requests, like Add ability to browse classical by various categories of performer or Artists / Composers / Perfomers? - if the demand adds up, maybe a next release will provide us with some improvement in this regard.
Also, it’s not possible to browse all artists (performers) like those primary artists - that has been requested by others but didn’t made it into roon yet (?).