Role capabilities issue

I solved the issue!

If you create a new CPT with the function register_post_type

You have to add this line in the array with arguments

'map_meta_cap' => true,

Now you can set capabilities to a role like below

add_role('owner', 'Eigenaar', 
    array(
        'read'                  => true,
        'publish_agendas'       => true,
        'edit_agenda'           => true,
        'edit_agendas'          => true,
        'delete_agenda'         => true,
        'delete_others_agendas' => true,
        'delete_others_agenda'  => true
    )
);

add_role('employee', 'Personeel', 
    array(
        'read'                  => true,
        'publish_agendas'       => true,
        'edit_agenda'           => true,
        'edit_agendas'          => true,
        'delete_agenda'         => true,
        'delete_others_agendas' => false,
        'delete_others_agenda'  => false
    )
);