Get a list of the roles supported. NOTE: the "next" role is automatically supported,
and the "none" role (for SOAP 1.2) is automatically disallowed. The roles returned
should only be the non-standard ones, since the ultimate destination role is also
handled by the isUltimateDestination method below.
a List containing URI Strings, one per custom role supported, or null
Are we the ultimate destination?
true if this is the ultimate destination, false if an intermediary.