WP_Roles::remove_role( string $role )

	public function remove_role( $role ) {
		if ( ! isset( $this->role_objects[$role] ) )
			return;

		unset( $this->role_objects[$role] );
		unset( $this->role_names[$role] );
		unset( $this->roles[$role] );

		if ( $this->use_db )
			update_option( $this->role_key, $this->roles );

		if ( get_option( 'default_role' ) == $role )
			update_option( 'default_role', 'subscriber' );
	}