Preheat oven to 425°F (220°C).
Wash and dry all vegetables, then cut into similar-sized pieces.
Place vegetables in a large bowl.
Drizzle with olive oil and toss to coat evenly.
Add garlic powder, paprika, salt, and black pepper. Toss well.
Spread vegetables in a single layer on a baking sheet.
Roast for 15 minutes without stirring.
Remove and toss vegetables, then return to oven.
Roast another 10 to 15 minutes until tender with crispy edges.
Remove from oven and add lemon juice or parmesan if desired.
Serve immediately.