fix pk lookups
diff --git a/plstackapi/core/api/roles.py b/plstackapi/core/api/roles.py
index 6c61e25..b243d78 100644
--- a/plstackapi/core/api/roles.py
+++ b/plstackapi/core/api/roles.py
@@ -6,6 +6,8 @@
  
 
 def _get_roles(filter):
+    if isinstance(filter, StringTypes) and filter.isdigit():
+        filter = int(filter)
     if isinstance(filter, int):
         roles = Role.objects.filter(id=filter)
     elif isinstance(filter, StringTypes):