Toss the cauliflower in the oil with salt and pepper, arrange in a single layer on a baking sheet and roast in a preheated 400F oven until lightly golden brown, about 20-30 minutes, mixing half way through.Puree everything in a food processor and pour into a baking dish.
Bake in a preheated 350F oven until the sides are bubbling and the top is lightly golden brown, about 20-30 minutes.