To a large 18 x 26-inch baking sheet, add your prepared brussels sprouts and sweet potatoes. Add the olive oil, salt, and pepper, and toss to coat. If you're adding any optional toppings, add them now, too. Then, spread the vegetables out in a single layer.
2 tablespoons extra-virgin olive oil, ½ teaspoon salt, ½ teaspoon black pepper, 2 cloves garlic, 2 teaspoons lemon juice, ½ teaspoon garlic and/or onion powder, 2 large shallots, 2 tablespoons unsalted butter, 2 tablespoons grated Parmesan cheese or Nutritional Yeast