This is a great make ahead dish and combining fresh with frozen vegetables works great!
Preheat oven to 400 degrees F.
Slice potatoes in half then chop into good size chunks (a fork serving). Peel if you want the carrots then slice about 1 inch thick. Lay all on a baking sheet and drizzle with olive oil then season with salt, pepper and about 2 teaspoons of rosemary. Roast for 25 minutes.
Add broccoli, cauliflower and red onion to a large baking dish. Drizzle with olive oil then season with salt, pepper, a teaspoon or more of rosemary, thyme, parsley and garlic powder. Add to the oven for 10 minutes.
Toss in the potatoes and carrots in the baking dish with the other vegetables and toss around. Taste for any additional seasonings. Lower oven temperature to 350 degrees F. and bake for 20 minutes.
Drizzle with oil before serving or sprinkle freshly grated parmesan cheese.