To find information in the data dictionary concerning roles, the following views are beneficial:
DBA_ROLES provides information on all the roles that exist in the database.
DBA_ROLE_PRIVS provides information on all the roles granted to users and roles.
ROLE_ROLE_PRIVS provides information on all the system roles granted to roles.
DBA_SYS_PRIVS provides information on all the system privileges that have been granted to users and roles.
ROLE_SYS_PRIVS provides information on all the system privileges that have been granted to roles.
ROLE_TAB_PRIVS provides information on all the system object privileges that have been granted to roles.
SESSION_ROLES provides information on all the roles that the currently logged-in user has enabled.