A fan-turbine rotor assembly includes a diffuser section (114) which turns and diffuses the airflow from a radial core airflow passage (80) toward an axial airflow direction. Diffuser flow passages communicate with the diffuser passages (144) at a location which reduces separation of the airflow as the airflow is turned from the radial core airflow passage (80) toward an axial airflow direction through airflow aspiration at the potentially turbulent locations.