Preheat oven to 375°F and grease a 9x13-inch baking dish. Toss broccoli, cauliflower, and carrots with a drizzle of olive oil, spread on a baking sheet, and roast for 15 minutes until tender.
Cook macaroni according to package directions until al dente, adding frozen peas during the last 2 minutes of cooking. Drain and set aside.
In a large pot, melt butter over medium heat. Whisk in flour and cook for 1-2 minutes until paste forms.
Gradually add milk, whisking constantly, and cook until sauce thickens enough to coat the back of a spoon, about 7 minutes.
Remove from heat and stir in white cheddar, Monterey Jack, and half the Parmesan until melted and creamy.
Add garlic powder, onion powder, salt, and pepper, then fold in the roasted vegetables.
Combine cheese-vegetable sauce with cooked macaroni and peas, mixing until everything is evenly coated.
Transfer to prepared baking dish and top with breadcrumbs mixed with remaining Parmesan cheese.
Bake for 25-30 minutes until bubbly around the edges and golden brown on top. Let rest 5 minutes before serving.