Preheat the air fryer: Set your air fryer to 390–400°F (200°C).
Preheating for 3–5 minutes helps the vegetables crisp faster.
Prep the vegetables: Cut everything into similar, bite-sized pieces. Keep dense vegetables (broccoli, cauliflower) a touch smaller than softer ones (zucchini) for even cooking.
Season: Add the vegetables to a large bowl. Drizzle with olive oil, then sprinkle in garlic powder, onion powder, Italian seasoning, smoked paprika, salt, pepper, and red pepper flakes if using.
Toss well until evenly coated.
Arrange in the basket: Place the vegetables in a single layer in the air fryer basket. A little overlap is fine, but avoid piling them high for best browning. Cook in batches if needed.
Air fry: Cook for 10–14 minutes, shaking the basket halfway. Start checking at 8 minutes.
The vegetables are done when edges are browned and the centers are tender.
Finish and serve: Transfer to a bowl. Add lemon juice, zest, parsley, or Parmesan if you like. Taste and adjust salt and pepper.
Serve hot.