Preheat the oven: Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper or foil.
Toss the squash: In a large bowl, combine the summer squash rounds, olive oil, lemon zest, lemon juice, grated Parmesan cheese, salt, and pepper. Toss well to ensure the squash is evenly coated with the mixture.
Arrange on the baking sheet: Transfer the seasoned squash to the prepared baking sheet, spreading them out in a single layer. Make sure they are not overcrowded to allow for even roasting.
Roast the squash: Place the baking sheet in the preheated oven and roast for 15-20 minutes, or until the squash is tender and slightly browned around the edges. Keep an eye on them and toss halfway through cooking to ensure even browning.
Garnish and serve: Once roasted, remove the squash from the oven and garnish with freshly chopped parsley or basil if desired. Serve as a side dish or use it as a flavorful addition to your favorite pasta dish.