Preheat oven to 180°C/360°F.
Place sweet potatoes in a single layer in a roasting tin.
Place butter and coconut sweet chilli in a saucepan over medium-high heat and cook, stirring for 2-3 minutes. Remove from heat and pour over the potatoes. Use tongs to toss to coat evenly. Cover with foil and roast for 30 minutes. Then remove foil, gently toss the potato pieces. And roast for a further 20-30 minutes or until tender and sticky.