[Plugin: Role Scoper] get associated roles to post in loop?

now I would like to output every user from the user group subscriber of each post in the loop

I’m not sure if you are referring to a custom-defined role group or a WP role. These could be helpful:

$users = ScoperAdminLib::get_group_members( $group_id );

global $scoper;
$users = $scoper->users_who_can( 'read', COLS_ALL_RS, 'post', $post_id );