Report of number of users per role

Need to grab from config the full list of roles, to give the full role names along with the machine names, and to highlight the roles with no users. But other than that here's the query:

SELECT roles_target_id "role", COUNT(entity_id) "user count" FROM user__roles GROUP BY roles_target_id;

Each role could link to the admin/people page filtered to that role.

Then a supplementary report listing any people who are in only one role might be of interest?