Preheat oven to 415 degrees F. Line a large rimmed baking sheet with foil and spritz with non-stick spray.
In a large bowl combine the diced sweet potato and cauliflower and toss with 1 tbsp olive oil, ½ tsp salt and ¼ tsp black pepper. Toss to coat and then spread into an even layer on the baking sheet. Roast for 10 minutes. Stir the potatoes and cauliflower and then push to one side of the pan.
Meanwhile, combine the remaining vegetables in the same large bowl and toss with 1 tbsp olive oil, ½ tsp salt, ¼ tsp black pepper, ½ tsp garlic powder, ½ tsp onion powder and ½ tsp Italian seasoning.
Add the seasoned vegetables to the pan with the sweet potato and cauliflower, making sure to give all the vegetables plenty of room, allowing them to roast evenly. Continue roasting for an additional 15 to 20 minutes, stirring the vegetables again halfway through, until they are tender.