Add Role inherits?

You must set to true for them to take affect. If you do not specify true they all default to NULL which in turn basically makes them false.

So to create a roll that allows pages only:

add_role('page_editor', 'Page Editor', array(
    'read' => true,
    'edit_others_pages' => true,
    'edit_pages' => true,
    'edit_published_pages' => true,
    'delete_pages' => true,
    'delete_published_pages' => true,
    'publish_pages' => true,
));