Pre-heat the oven to 220°c.
Add the cubed potatoes to a pan of boiling water and parboil for 10 minutes. They should still be firm when you take them out. Drain off the water.
Spray a baking tray with low calorie cooking spray and spread the potato cubes onto the tray. Spray again with low calorie cooking spray and sprinkle over the garlic and rosemary.
Place the potatoes in the middle of the hot oven for 20-25 minutes, until golden and crispy on the outside and soft in the inside. Serve as a side with your favourite main.