WordPress at a glance
action is not described

add_user_role action-hook . WP 4.3.0

Fires immediately after the user has been given a new role.

Usage

add_action( 'add_user_role', 'action_function_name_7010', 10, 2 );
function action_function_name_7010( $user_id, $role ){
	// action...
}
$user_id(int)
The user ID.
$role(string)
The new role.

Where the hook is called

WP_User::add_role()
wp-includes/class-wp-user.php 534
do_action( 'add_user_role', $this->ID, $role );

Where the hook is used (in WP core)

Does not used.