Preheat the oven to 425 degrees F.
In a large mixing bowl, combine cauliflower and broccoli florets. Add sliced onions to it.
In a small bowl, combine olive oil, Sal, garlic and herbs. Pour mixture over veggies and toss.
Spread veggies on to a baking sheet. Sprinkle Parmesan cheese over veggies.
Cook in preheated oven for 20 - 25 minutes until veggies begin to brown on the edges.