Preheat the oven to 400°F.
Wash and chop the broccoli, carrots, onion, and potatoes.
In a bowl, mix the olive oil, cornstarch, mixed herbs, garlic powder, pepper, and salt.
Add the chopped vegetables to the bowl and toss to coat them evenly.
Spread the vegetables on a baking sheet lined with parchment paper.
Roast in the preheated oven for 35-45 minutes, or until the vegetables are tender and lightly browned.
Serve hot and enjoy!