Opencast's ACL editor is supposed to filter certain roles which are not meant to govern access to resources, but rather to grant users certain capabilities. Most prominently these are the `ROLE_UI_*` type of roles and `ROLE_ADMIN_UI`.
This works correctly in some instances of the editor, for exmaple when creating a new ACL template or editing an existing event and/or series, and also when creating a new series. It does *not*, however, when creating a new event, i.e. all roles are visible in the ACL editor of the new event wizard.
See also here for a related discussion: https://groups.google.com/a/opencast.org/forum/#!topic/dev/6a4nSsBuzZg