Theoretically you can do this for ABAP UME users, but there is a big "gotcha":
Java systems don't have the same client concept as an ABAP system, and what is behind the ABAP role mapping on the Java side is not known to the ABAP system and may even differ.
The consequence is that if you point multiple Java UME's to one ABAP CUA system's client dependent user store... then assigning a role to the user will assign it in all Java systems, depending on what is mapped behind it.
Using a <SID> naming conventions for Java systems within the ABAP roles is not scalable and there are many standard roles anyway.
A consideration I have heard of was to use a multiple of ABAP clients, one for each Java system, but that might not be scalable as a solution either unless you are sure you will only have limited number of Java landscapes and systems.
Instead of trying to support such a workaround yourself, you will be better off looking into an IdM. See the thread at the top of the forum page about Identity Management (IdM).
Cheers,
Julius
