Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper. Measure out the vegetables and chop them into even-sized pieces for uniform roasting.
In a large mixing bowl, combine the chopped vegetables with olive oil, toasted sumac, and salt. Use a spatula to toss until all pieces are evenly coated and the spices are well distributed.
Spread the coated vegetables in a single layer on the prepared baking sheet, ensuring they are not crowded to promote even roasting.
Roast the vegetables in the preheated oven for 25-30 minutes, or until they are tender and slightly browned at the edges, with visible caramelization.
Remove from the oven and check for doneness. The vegetables should be soft with crispy edges. Serve immediately, garnished if desired.