Roughly chop the kale. When the veggies have been cooking for 20 mins, remove the vegetable tray from the oven, turn the veggies over and push to one side. Add the kale to the tray, sprinkle with a pinch of salt and drizzle with 1/2 tsp of oil. Return to the oven and cook for a further 5 mins until the kale starts to crisp.