Oracle : How to grant to a ROLE the ability to grant a ROLE to a USER?
works fine for me on 11.2:

CONN SYSTEM/&lt;&gt;
CREATE ROLE admin_role;
Grant create role to ADMIN_ROLE with admin option;
Grant create user to ADMIN_ROLE with admin option;
CREATE USER john IDENTIFIED BY john;
Grant admin_ROLE to john;
GRANT CONNECT, RESOURCE TO john;
CREATE USER john2 IDENTIFIED BY john2;
GRANT CONNECT, RESOURCE TO john2;

CONN john/john
CREATE ROLE test_role;
grant test_role TO john2;

DROP ROLE ADMIN_ROLE;
DROP ROLE TEST_ROLE;
DROP USER john CASCADE;
DROP USER john2 CASCADE;


Grant, executed in 10 ms

Try redoing it, you probably missed an admin option when you tried for the first time.
Drop everything.