Position a rack in the upper third of the oven and preheat to 425°F. Drizzle 1 tablespoon of the olive oil over the sheet pan and place it in the oven while it preheats — a hot pan is what makes the gnocchi crispy from the first minute.

In a large bowl, toss the bell peppers and red onion wedges with the remaining 2 tablespoons olive oil, the garlic, Italian seasoning, salt, black pepper, and red pepper flakes (if using) until evenly coated.

Carefully pull the hot pan from the oven. Spread the gnocchi (straight from the package — no boiling) in a single layer, then scatter the seasoned peppers and onion around them. Pinch the sausage into 1-inch pieces and distribute them over the pan. Give everything one good toss right on the pan so the gnocchi picks up some oil.

Roast until the gnocchi are golden and crisped at the edges, the sausage is cooked through with no pink remaining, and the peppers and onion are caramelized at the corners. Toss everything once halfway through so all sides get color.

The sausage must reach 165°F internally — cut the largest piece open to confirm no pink remains. The gnocchi are done when puffed, golden, and crisp on the outside.

Shower the hot pan with half the Parmesan so it melts into the crispy bits, then scatter the basil over the top. Serve straight from the pan with the remaining Parmesan passed at the table.