Preheat oven to 400°F (200°C). In a large bowl, toss cubed butternut squash and sliced sweet potatoes with olive oil, minced garlic, dried sage, thyme, salt, and black pepper. Spread evenly on a parchment-lined baking sheet and roast for 25–30 minutes until tender. Reduce oven temperature to 375°F (190°C).

Sauté spinach in a skillet with a splash of olive oil for 2 minutes until wilted. Squeeze out all excess moisture using a towel. In a bowl, mix ricotta, crumbled feta, and half of the mozzarella until creamy. Fold in the squeezed spinach.

Grease a 9×13-inch baking dish. Spread a thin layer of cheese mixture on the bottom. Add a layer of noodles, followed by half the cheese-spinach blend, half the roasted squash/sweet potatoes, and half the chopped walnuts. Repeat for a second layer.

Top with the remaining noodles, thin cheese layer, reserved roasted squash cubes, remaining chopped walnuts, and fresh sage leaves.

Cover loosely with foil and bake at 375°F (190°C) for 25 minutes. Uncover and bake for an additional 15–20 minutes until golden brown and bubbly.

Let rest for 15 minutes before slicing into 8 neat squares.