Rollback is not intended to undo deleted objects. It can rollback changes that have not been committed yet.
You could also change the object and remove the association instead of removing the objects. This way the question or section won’t show on your page. When you want to undo the delete, you just rollback the changes and the association will be set back to it's original state. Add a refresh and the section or question should appear on your page again.
Also see: https://docs.mendix.com/refguide/rollback-object/
Hope this helps!