Preheat oven to 425°. Cut broccoli florets in half through the stem so they'll lie flat while roasting for nice, even browning. Divide broccoli between 2 large rimmed baking sheets.
Drizzle 1/4 cup oil over broccoli, sprinkle with salt and pepper, and turn until well coated.
Arrange florets in a single layer, flat side down, and roast, switching pan positions and turning broccoli with tongs halfway through cooking, until tender crisp and beginning to brown on the bottom, 10 to 15 minutes. Drizzle with oil.