--- admin.module.orig
+++ admin.module
@@ -374,6 +374,16 @@
           $block->module = $module;
           $block->delta = $delta;
           $block->cache = is_numeric($cache) ? $cache : BLOCK_NO_CACHE;
+          // Get allowed rids for this block.
+          $result = db_query("SELECT rid FROM {blocks_roles} WHERE module = '%s' AND delta = '%s'", $module, $delta);
+          $block_rids = array();
+          while ($rid = db_result($result)) {
+            $block_rids[] = $rid;
+          }
+          // Don't display the block if it is restricted to role(s) and the current user does not belong to one of the roles.
+          if (count($block_rids) && !count(array_intersect($block_rids, array_keys($GLOBALS['user']->roles))) && $GLOBALS['user']->uid != 1) {
+            continue;
+          }
         }
         if (!empty($block)) {
           if ($_SERVER['REQUEST_METHOD'] == 'GET' && $cid = admin_block_get_cache_id($block)) {