Preheat the oven to 425 degrees F. Optional to line a large baking sheet with foil or parchment paper.
Add the broccoli and cauliflower florets in a large bowl and drizzle with oil, garlic, and salt and pepper. Toss to coat; use your hands if you need to.
Arrange the veggies in a single layer on the baking sheet, spreading them out. Bake for 20 minutes or until the edges are browned.
Halfway through the cooking time, move the veggies around on the pan for more even cooking.
Toss halfway through for more even cooking - optional but works better.
Season to taste (if you need more salt and pepper). Serve!