Preheat the oven to 400F. Pat the chicken thighs dry with paper towel, cut the sweet potato into wedges or sticks, and separate the cauliflower into florets. Put the chicken thighs on a parchment-lined rimmed baking sheet, drizzle with oil and sprinkle with salt and pepper. Put the veggies in a bowl, drizzle with oil and toss to coat, then arrange them on the sheet around the chicken.
Roast for 25-35 minutes, stirring things around once or twice, until the chicken is cooked through and the veggies are golden. Serves 4.