Preheat oven to 375°F; grease a 9x13-inch dish. Toss broccoli, cauliflower, and carrots with a drizzle of oil; spread on a baking sheet. Roast 15 minutes until tender.
Cook macaroni according to package until al dente, adding peas in last 2 minutes; drain and set aside.
Melt butter in a large pot over medium; whisk in flour and cook 1-2 minutes until paste forms.
Gradually whisk in milk constantly; cook about 7 minutes until sauce coats a spoon's back.
Remove from heat; stir in cheddar, Monterey Jack, and half the Parmesan until melted and creamy.
Add garlic powder, onion powder, salt, and pepper; fold in roasted vegetables.
Mix sauce with macaroni and peas to coat evenly.
Transfer to dish; top with breadcrumbs mixed with remaining Parmesan.
Bake 25-30 minutes until edges bubble and top is golden brown; rest 5 minutes before serving.