Preheat the oven. Set it to 425°F (220°C). A hot oven is key for browning and crisp edges.
Prep the pan. Line a large rimmed sheet pan with parchment paper or foil for easier cleanup. If you have two smaller pans, use both to avoid crowding.
Cut the vegetables evenly. Aim for similar-sized pieces: potatoes about 1-inch, peppers in thick strips, onion in wedges.
Even sizes mean even cooking.
Toss with oil and seasoning. In a large bowl, combine potatoes, peppers, onion, broccoli, and zucchini (if using). Add olive oil, salt, pepper, garlic powder, smoked paprika, and Italian seasoning. Toss until everything is well coated.
Arrange on the sheet pan. Spread the veggies in a single layer, cut sides down when possible.
Nestle the sausage pieces throughout. Do not overcrowd—space helps caramelization.
Roast. Place in the oven and cook for 25–30 minutes, flipping the veggies and sausage halfway. If using raw sausage links, roast them whole and slice after cooking for juicier bites.
Check for doneness. Potatoes should be tender when pierced, and edges should be browned. Sausage should be sizzling and cooked through (165°F/74°C for poultry sausage; 160°F/71°C for pork).
Finish with brightness. Squeeze fresh lemon over the pan and sprinkle with parsley.
Taste and adjust salt, pepper, or red pepper flakes.
Serve. Enjoy as is, or pair with a simple green salad, a side of rice or quinoa, or warm crusty bread to soak up the juices.