I tried the same but it seams it is not yet supported (Alpha 3).
The only way I found is to copy all the common properties with the annotations to each root class.
I will leave that solution as long as the @MappedSuperclass Annotation is not supported and resolve the problem then by that mapping. It is exactly what the jboss-ejb3 thing needs next.
Pardon, @EmbeddedSuperclass is same as @MappedSuperclass and is supported