Role problem of PostgreSQL

I want to create a role named cp with some defined privileges, then we will create some other roles which will be granted with cp role. I know Oracle can do this job. For examle grant resources to user_name; which means grant resources role to a user. I do the follwing test in PostgreSQL, but it does not work. Any body know this?

--create role cp and grant privilege
postgres=# create role cp login nosuperuser nocreatedb nocreaterole
           noinherit encrypted password 'cp';
CREATE ROLE

postgres=# grant connect on database skytf to cp;
GRANT

postgres=# \c skytf skytf;
You are now connected to database "skytf" as user "skytf".

skytf=> grant usage on schema skytf to cp;
GRANT

skytf=> grant  select on skytf.test_1 to cp;
GRANT


--create role cp_1, and grant cp role privilege to cp_1
skytf=> \c postgres postgres
You are now connected to database "postgres" as user "postgres".

postgres=# create role cp_1 login nosuperuser nocreatedb nocreaterole
           noinherit encrypted password 'cp_1';
CREATE ROLE

skytf=# grant cp to cp_1;
GRANT ROLE


--test cp_1
skytf=# \c skytf cp_1;
You are now connected to database "skytf" as user "cp_1".

skytf=> select * from skytf.test_1 limit 1;
ERROR:  permission denied for schema skytf
LINE 1: select * from skytf.test_1 limit 1;