step 1 Heat oven to 200C/180C fan/gas 6. Toss the sweet potato chunks with the olive oil and some seasoning, and spread on a baking parchment-lined baking sheet. Roast for 30 - 35 mins until tender and golden. Cool at room temperature. step 2 When just about cool whisk together all the dressing ingredients with a little more seasoning and gently toss through the potato chunks – use your hands to avoid breaking them up.