How to get user's role?

Hi all,

I want to get what roles/groups that the current user is member of.
I tried to use the following commands but they both returned no rows.

SELECT * FROM information_schema.enabled_roles
SELECT * FROM information_schema.applicable_roles

Anybody know how to solve this ? or anybody has a certain
function that look up for user's roles/groups ?

Thanks in advanced,

Armen