Deleting Database Roles
A superuser can delete a role with the DROP ROLE statement.
Note that if any user or other role has been assigned the role you are trying to delete, the DROP ROLE statement fails with a dependency message.
=> DROP ROLE administrator;
NOTICE: User Bob depends on Role administrator
ROLLBACK: DROP ROLE failed due to dependencies
DETAIL: Cannot drop Role administrator because other objects depend on it
HINT: Use DROP ROLE ... CASCADE to remove granted roles from the dependent users/roles
Supply the optional CASCADE parameter to drop the role and its dependencies.
=> DROP ROLE administrator CASCADE;
DROP ROLE