A few notes on this plugin (it's documentation is horrible):
It won't use the template.vm file unless you specify it, like
roll-gen-template.vm
For creating a war:
If you want to use the JnlpDownloadServlet (the standard one java provides) to serve up the files instead of the above code (and have the plugin generate a working version.xml file for it to use, etc.), basically you need to create a new project of type war and target the jnlp-download-servlet goal (it doesn't seem to support creating a war with classes from the current pom project) then, instead of a single section, you'll have the section instead, which can list multiple jar dependencies. You may need to modify your web.xml file as well.
http://www.mojohaus.org/webstart/webstart-maven-plugin/jnlp-mojos-overview.html has an example pom for
If you have additional comments feel free to edit this, it is a community wiki.