Cut each chicken fillet into 3 pieces and place into bowl with sumac, gently coat and massage sumac into chicken then place bowl in fridge. Chop kumara and pumkin into wedges and place in large roasting pan with bruised garlic cloves and rosemary sprigs. Take chicken from fridge and scatter into roasting pan with vegies, season with salt and pepper and coat with olive oil. Gently toss with your hands to make sure all chicken and vegies are coated in oil then place in oven for 35 mins til vegies start to colour and chicken cooked through.