I asked a similar question recently, but I wanted an answer specifically for Drupal Views. I'm broadening my scope now.
I thought I had an answer to my question via Case Reports. I can show only those cases without managers by implementing the "Case Role(s)" filter and setting it to "Is not one of" "Case Manager". This gives me the results I expect. However, I can't actually navigate to individual cases from the report. Instead when I click on the case subject, a modal window pops up that shows very little information about the case.
I would like to have a list of cases without managers with links to manage the case.
I'd prefer a built-in civi solution, but I'm fair with PHP and not averse to some custom coding if need be.