Preheat oven to 400°F.
Cut cauliflower into florets and slice up the stem.
Toss cauliflower pieces in olive oil, salt, and pepper to coat.
Lay florets and stem slices onto a silicone baking mat on a baking sheet.
Place baking sheet with cauliflower pieces into the oven for 15 minutes.
Stir cauliflower and bake for another 10 minutes until edges are lightly browned.