Preheat the oven: Preheat the oven to 400°F. Line a large baking sheet with parchment paper.
Combine ingredients: Prepare Place all the veggies (tomatoes excluded) and sausage on the prepared sheet pan. Drizzle the olive oil all over everything, then add the Italian seasoning, garlic powder, salt, pepper and toss everything together well. Arrange them so that they are one even layer over the baking sheet, to ensure even cooking.
Bake: Transfer the baking sheet to the oven and bake for 15 minutes.
Add tomatoes: Carefully remove the baking sheet from the oven and add the tomatoes. Flip or stir all the ingredients around. Return the baking sheet to the oven and bake for another 20 minutes or until the vegetable are crisp-tender and potatoes are fork tender.
Finish and serve: If desired, sprinkle with freshly grated Parmesan cheese as soon as they come out of the oven and serve over rice or quinoa.