There are various plants that are heat and sun exposure resistant that still display a lovely lush appearance. Stick to natives, and stick to the natives for your area. I would plant a variety of taller plants to add shade and coolness, and then you can experiement with flowers etc using the canopy of shade you have created. The heat from the roxks will decrease with added vegitation.
I cant go past native wattles, bottlebrushes and kangaroo paws. They encourage bees, birds, flower regularly and are so Australian.