I find it's better to cut the cauliflower into flat slices rather than lumpy florets so you have as much surface area in contact with the hot pan as possible for maximum browning. Cut the cauliflower into half-inch-thick slabs and cut the core out of the middle slices. They will naturally separate into bite-sized pieces while cooking.
2 Tbsp. olive oil
1 cauliflower, sliced into 1/2-inch thick slabs
Salt and freshly ground black pepper to taste
Preheat the oven to 400° F. Coat a sheet pan with a thin film of olive oil and sprinkle with a little salt and pepper. (You might need two pans depending on the size of your cauliflower.)
Lay the cauliflower in a single layer on the pan. No crowding. You don't want the pieces to sit too closely together or they'll steam more than roast. Drizzle with additional oil and sprinkle with salt and pepper. Roast the cauliflower on the bottom rack of the oven for 10 to 15 minutes or until the bottoms turn a golden shade of brown. Flip and cook 10 to 15 minutes more until the other side browns and the vegetables are tender but not mushy. Serve hot.