Version 4.5.1 of User Role Editor is the critical bug fix release. You did not install version 4.5 yet, as the next 4.5.1 update followed. The bug with multi-site super-admin access to the User Role Editor was fixed. Version 4.5. showed message “Insufficient permissions to work with User Role Editor” until add “manage_network_users” capability to the “Administrator” role. It is enough now to be the “Superadmin” at multi-site network.