Preheat the oven to 350˚F.
Slice the cauliflower florets lengthwise in half or quarters, so they are about a ¼ to ½-inch-thick. Place in a large bowl and set aside.
In a mortar and pestle, crush the cumin seeds and salt together until finely ground. Add to the cauliflower along with the olive oil and turmeric. Toss to evenly coat the cauliflower pieces.
Arrange the cauliflower in a 9 x 13-inch non-stick roasting pan, and transfer to the preheated oven. Roast, tossing once half way through, until the edges of the florets are golden and the smaller pieces are crisp, approximately 45 minutes. Remove from the oven and serve immediately.