So where is the problem? HTML files will be handle by apache and war, ear and so on by JBoss. The only thing you may do is configuring apache to foward some request to JBoss. You may use mod_proxy_ajp for this purpouse.
The root context is handled by server/xxx/deploy/jboss-web.deployer/ROOT.war - you can place your html file in there.
I put html file as suggested by in that location.