This may or may not answer your question, but I recently discovered a rails plugin called jrails which integrates jquery into rails very similar to the way prototype comes in rails.
installing jrails allows you to use this: <%= javascript_include_tag :defaults %> to include jquery library files and there are other benefits and integrations, some of which i am pretty sure include helper methods for rjs. so i would try looking into the details for jrails... hope that helps... J