Preheat the oven to 400°F. Cut the delicata squash in half lengthwise, scoop out the seeds, and cut into half-moon slices. Toss the slices with olive oil, salt, and pepper, then spread on a baking sheet. Roast for 25 minutes until tender and lightly browned.

While the squash roasts, bring a large pot of salted water to a boil. Cook the jumbo shells until just al dente, then drain and set aside to cool slightly.

Mash the roasted squash in a bowl until mostly smooth with a few small chunks remaining. Stir in the ricotta, 1/2 cup of the Parmesan, and a pinch of salt and pepper until combined.

Spoon the squash filling into the cooked shells and arrange them in a baking dish. Sprinkle the remaining 1/4 cup Parmesan over the top.

Melt the butter in a skillet over medium heat. Add the minced garlic and cook for 30 seconds, then add the sage leaves. Continue cooking until the butter turns golden brown and the sage crisps, about 3 to 4 minutes.

Pour the brown butter and sage over the stuffed shells. Serve right away.