Add new roles problems

I’m trying to check if it is possible to add a new role for users

Ex: Sellers (A user level where they can see the sales progress, donwload .pdf, etc.)

I went in my function.php file and I wrote this down.

add_role( 'sellers', 'Seller', array(
    'read' => true, // True allows that capability
    'publish_pages' => true,
	'read_private_pages' => true,
	'publish_posts' => true,
	'edit_posts' => true,
	'read_private_posts' => true
	));

It actually works well for the new user.. But when I try to see the “private posts or things like that”, I see nothing..