This template is not blank, it adds a little icon in the top-right corner. See?
This template adds your username to Category:Wikipedia rollbackers.
Place {{Rollback topicon}} anywhere on your user page to indicate that you have the Rollback user right.
This icon is based on {{Top icon}}.
{{Rollback topicon| nocat = yes = disables the automatically added category (default = no)| sortkey = = custom sorting - the relative position of topicons on the page (alphabetical)| link = = custom link target (default = Wikipedia:Rollback)}}