Can I audit all actions of a database role?

I know from AskTom that we can audit all actions of a particular user account, e.g.:

create audit policy test_audit_policy  actions all  when q'!sys_context('userenv', 'session_user') = 'SUSPICIOUS_USER'!'  evaluate per session  container = current;

What I would like to do instead is to audit all actions performed when a particular database role has been set. So, it wouldn't matter whether it's Mike Meyer or Sue Smith; their actions would not be audited until they set the particular role, and from that moment on their actions in the session would be audited.

Is this possible? If so, how?