Preheat the oven to 400 degrees. Drizzle 3 tsp. oil onto a baking sheet. Sprinkle with turmeric. Spread the cauliflower on the pan in one layer. Drizzle with remaining oil. Add the salt and several grinds of pepper. Mix with your hands to coat the florets.
Roast the cauliflower for 20 minutes. Stir the cauliflower, roast 5 minutes and then stir again. Continue roasting until the cauliflower is almost soft and some tips are dark brown, about 5 minutes longer. Cool the califlower on the pan. Serve warm or at room temperature.