I used the following, and it always sends the last node's id to me. no matter which node I selected.

 <rich:tree style="width:300px"
 value="#{desktopBean.templateRoot}"
 var="item" nodeFace="leaf">
 <rich:treeNode type="leaf"
 onselected="saveFolderSelection();">
 <a4j:jsFunction name="saveFolderSelection">
 <a4j:actionparam name="folderPath"
 value="#{item.id}"
 assignTo="#{desktopBean.folderPath}"
 noEscape="false"/>
 </a4j:jsFunction>
 <h:outputText value="#{item.name}"/>
 </rich:treeNode>
 </rich:tree>