Line 110 of rollout.module:

$sites_dir = dirname($GLOBALS['_SERVER']['SCRIPT_FILENAME']) . '/sites'; // FIXME - Is the sites folder always relative to index.php in this way

Results in an empty array for me - in fact, a print_r($GLOBALS['_SERVER']) results in an empty array as well.

Changing the code to reference $_SERVER - just like rollout_server.module does corrects the problem:

$sites_dir = dirname($_SERVER['SCRIPT_FILENAME']) . '/sites'; // FIXME - Is the sites folder always relative to index.php in this way