OpenSearch was created by Amazon and is used by Internet Explorer 7, Firefox 2, and other applications.
Cut and paste the following into your browser's location bar to add the RocWiki search provider to Firefox or IE:
javascript:window.external.AddSearchProvider('http://rocwiki.org/OpenSearch?sendfile=true&file=OpenSearch.xml')
(Maybe one of the admins can make that a javascript link, since I haven't found a way.)
For Firefox, you can also try this.