Preheat your oven to 425°F and line a baking sheet with foil lightly misted with cooking spray. In a large bowl, toss the cubed butternut squash and apples with 2 tablespoons olive oil, 1/2 teaspoon salt, 1/4 teaspoon black pepper, 1 tablespoon maple syrup, dried sage, and Herbes de Provence until everything is evenly coated.

Spread the squash mixture onto your prepared baking sheet in a single layer. Roast for 35 minutes, stirring every 10-12 minutes to ensure even caramelization. The squash is ready when it's fork-tender with golden-brown edges.

While the vegetables roast, heat a large skillet over medium-high heat with a drizzle of olive oil (about 1 tablespoon). Once the oil is shimmering (about 2 minutes), add the crumbled sausage and cook for 4-5 minutes until browned and cooked through. Transfer to a bowl and set aside.

Using the same skillet (add another tablespoon of oil if needed), add the sliced fennel and onion. Cook for 10-12 minutes, stirring occasionally, until deeply golden and almost jammy in texture. Add the caramelized vegetables to the bowl with the sausage.

Once the squash and apples finish roasting, switch your oven setting to broil. Transfer the roasted vegetables to a large bowl and gently fold in the sausage-fennel mixture along with the remaining tablespoon of maple syrup. Taste and adjust seasoning with additional salt and pepper if needed.

Spoon the mixture into a 9x13-inch baking dish and top with grated Gruyere cheese. Place under the broiler for 2-3 minutes, watching carefully to prevent burning, until the cheese is melted and golden. Garnish with fresh sage leaves before serving.