Preheat oven to 400 degrees F. Set a medium pot of salted water to boil. Prepare a large baking sheet by lining with aluminum foil and coating with a little olive oil or nonstick cooking spray.
Toss broccoli, red pepper, squash and carrots onto the baking sheet. Bake for 20 minutes, or until vegetables have softened. Remove from oven and set aside.
Once water is boiling, lower heat slightly and add pasta, cooking according to package instructions. Drain and set aside.
Meanwhile, heat oil in a large skillet over medium heat. Once hot, add garlic and cook 30 seconds. Whisk in flour and cook 1 minute. Gradually whisk in milk, stirring constantly until mixture is slightly thickened. Remove from heat. Stir in cheddar cheese until well distributed and melted. Add red pepper flakes, cayenne pepper, salt and pepper. Add macaroni and vegetables.
Place mixture in a large casserole dish and sprinkle with panko breadcrumbs. Place under the broiler in your oven (500 degrees) for 3-4 minutes, or until the top is golden brown.