Adjust the oven racks for roasting 2 trays. Preheat the oven to 450 degrees Fahrenheit.

Chop the vegetables: Chop the cauliflower and broccoli into florets. Chop the onion into 1/2-inch slices. Cut the sweet potato in half lengthwise, in half again lengthwise, and then cut each quarter into thin pie-shaped slices (see the photo). Chop the peppers into 1/2-inch strips, then cut the strips in half.

Line two baking sheets with parchment paper (we prefer this to silicone baking mats because it results in crispier veggies). Spread the vegetables evenly onto each sheet. Drizzle half the olive oil onto each tray, then with half the seasonings onto each tray. Mix with your hands until evenly coated.

Place into the oven and bake for 20 minutes (do not stir!). Remove the pans from the oven, rotate them, and roast another 10 minutes (for 30 minutes total) until tender and lightly browned on one side. Transfer to a serving bowl or dish and serve immediately.