I think you can remove the ROOT.war out of the jbossweb-tomcat50.sar dir and create your own and have it deployed instead.
Put the following in your jboss-web.xml file:
<jboss-web> ... <context-root>/</context-root> ... </jboss-web>
I found a simular solution to the problem (as the last statement)...
If one is deployed with an ear file, the application.xml can have the following statement: