Preheat oven to 425°F. Cook rice according to package directions, omitting salt and fat. Toss together squash, broccoli, bell peppers, black pepper, 2 tablespoons oil, and 3/4 teaspoon salt on a large rimmed baking sheet. Spread in an even layer. Bake vegetables, turning over halfway through, until tender and browned, about 25 minutes.