How to let user select role upon registration in Facebook-AWD?

The plugin offers an entry point for this manipulation:

$userdata = apply_filters('AWD_facebook_register_userdata', $userdata);

So, now it’s a matter of you filling up the fictional function in this example:

add_filter( 'AWD_facebook_register_userdata', 'user_role_wpse_87863', 10, 1 );

function user_role_wpse_87863 ( $userdata )
{
    $userdata['role'] = your_way_of_getting_the_role();

    return $userdata;
}

Related:

• About Hooks and Filters

• Actions and filters are NOT the same thing…