To create a new role use following command:
CREATE ROLE user WITH LOGIN ENCRYPTED PASSWORD 'password';
To change the role(e.g. give new permissions) run:
ALTER ROLE user WITH CREATEDB;
To list all roles:
\du
This will give you following output:
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
phil | Superuser, Create role, Create DB, Replication | {}
user | Create DB | {}
To delete a role run:
DROP ROLE user;
Read more here: https://www.postgresql.org/docs/8.1/static/sql-createrole.html