Is there a way to copy users or roles and their grants from one instance to
another? Perhaps using "exp full=y", then imp?

Do you want all users or just certain users? If all users then you can
use a full exp with rows=n to extract all DDL, grants, users, roles,
etc... and then import that.

You can use a user export for just one user's objects but this will not
get roles.

The create script for a role is fairly easy to generate from the
dictionary views or you can cut it out of a full exp dump with a little
editing code.

HTH -- Mark D Powell --