Preheat oven to 180C.Cut peeled sweet potatoes into 2cm chunks, and then place into an oven dish.Sprinkle the sweet potatoes with ½ teaspoon of chilli flakes, season with salt and pepper, then drizzle with 2 tablespoons of olive oil. Roast in the oven until the sweet potato is tender (about 20 minutes).Trim any excess fat off...