How to delete user roles?

$wp_roles = new WP_Roles(); // create new role object
$wp_roles->remove_role('name_of_role');

If you need to check the name_of_role use

$wp_roles->get_names();

you will get an array of name_of_role => Nicename of Role

Alternatively, you could use the global object $wp_roles

global $wp_roles;

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