I never run a JBoss installation installed as root.
It is a Java based server and I see no reason for that.
I alway install (unpack) and run the JBoss under a specific user. Often you do not have the root permission in a productive environment.
I'm not sure whether there are security leaks without applications, but a deployed application might damage the system if the process is with root access.
I'm not sure but I think you won't find such an installation document. But also there is no documentation that say you have to install with root access