WordPress at a glance
action is not described

wp_roles_init action-hook . WP 4.7.0

After the roles have been initialized, allow plugins to add their own roles.

Usage

add_action( 'wp_roles_init', 'action_function_name_9006' );
function action_function_name_9006( $this ){
	// action...
}
$this(WP_Roles)
A reference to the WP_Roles object.

Where the hook is called

WP_Roles::init_roles()
wp_roles_init
wp-includes/class-wp-roles.php 290
do_action( 'wp_roles_init', $this );

Where the hook is used (in WP core)

Does not used.