Preheat the oven to 425°F. Remove the outer leaves from the cauliflower and trim the base to create a flat surface. Slice each head into 2 to 3 thick steaks (about 1½ inches each). Arrange the slices in a single layer on a rimmed baking sheet. Brush both sides with olive oil and season with salt and pepper. Roast, turning once, until tender and golden, 25 to 30 minutes.