Block showing users of a specific role is only showing up for the administrator
My guess is that there is an access check somewhere that is failing. When logged in as user 1, it's impossible for a standard access check to fail, so this would be why you're seeing the block.

To solve this, try granting ALL permissions to RoleX (make sure you do not do this on a live site) and see if the block appears when you log in as the test user who has RoleX. If the block starts showing up, start disabling permissions a few at a time until you find which one is causing the issue.