Thanks for the information.
User Role Editor allows to see ‘Administrator’ role in the roles drop-down list under WordPress multisite in 2 cases:
1) user has ‘manage_network_users’ capability.
But this gives to a user access to the “Network Admin -> Users”.
2) ure_supress_administrators_protection filter returns true.
In this case be careful, as non-admin users with ‘list_users’, ‘edit_users’ capabilities will can to edit users with ‘Administrator’ role and create other users with ‘Administrator’ role. So use this filter just in case you do not plan to have such users at your site.