Preheat the oven: Set your oven to 425°F (220°C). A hot oven is key for caramelized edges and tender veggies.
Line a rimmed sheet pan with parchment for easier cleanup, if you like.
Prep the veggies: Cut everything into similar, bite-size pieces so they cook evenly. Potatoes should be about 1-inch chunks. Keep zucchini on the thicker side so it doesn’t overcook.
Season well: In a large bowl, toss the potatoes, peppers, onion, and broccoli with olive oil, salt, pepper, garlic powder, smoked paprika, and Italian seasoning.
Save the zucchini for later so it doesn’t get mushy.
Start the roast: Spread the seasoned veggies on the sheet pan in a single layer, leaving a little space between pieces. Roast for 15 minutes to give the potatoes a head start.
Add sausage and zucchini: Remove the pan, add the sliced sausage and zucchini, and toss gently right on the pan. Spread everything out again.
If the pan looks crowded, use two pans to prevent steaming.
Finish roasting: Return to the oven and roast for another 15–20 minutes, stirring once halfway through. Look for browned edges on the veggies and lightly crisped sausage.
Finish and serve: Drizzle with balsamic vinegar or a squeeze of lemon for brightness. Taste and adjust salt and pepper.
Sprinkle with chopped parsley or basil and serve hot.