You can check which roles have been granted to a user by querying user_role_privs.
A user who creates a role is also granted that role by default.
SQL> desc user_role_privs;
Name Type Description
USERNAME VARCHAR2(30) --Name of the user to whom the role has been granted.
GRANTED_ROLE VARCHAR2(30) --Name of the role granted to the user.
ADMIN_OPTION VARCHAR2(3) --Whether the user is able to grant the role to another user or role. Equal to YES or NO.
DEFAULT_ROLE VARCHAR2(3) --Whether the role is enabled by default when the user connects to the database. Equal to YES or NO.
OS_GRANTED VARCHAR2(3) --Whether the role was granted by the operating system.
SELECT * FROM user_role_privs;