Prep. Preheat the oven to 425F. Trim both ends off each delicata squash. Cut each in half lengthwise, scoop out the seeds, and slice them into 1/4-inch thick half-circles. Toss the squash with the oil, salt, and black pepper, and spread it out evenly on a large baking tray.
Roast. Roast the squash until it's golden brown in spots on both sides, about 25 to 30 minutes, flipping once halfway through.
Toast the hazelnuts. After you flip the squash, spread the hazelnuts out in an even layer on a small baking tray (or other oven-safe dish), and roast until light golden, about 5 to 10 minutes (on the rack alongside the squash). Cool, and then coarsely chop the hazelnuts.
Brown the butter. Meanwhile, add the butter to a small saucepan over medium heat. Once melted, add the rosemary sprigs and cook until the butter is light brown and smells nutty, about 5 minutes. Remove and discard the rosemary.
Serve. To serve, put the squash on a serving platter. Drizzle on the rosemary browned butter and sprinkle on the hazelnuts. Garnish with fresh rosemary if desired. Serve warm.
Notes
Squash Size: The delicata squash I used were about 1 to 1 1/4 pounds each.
Paleo Version: To make this recipe paleo, use ghee instead of brown butter.
Vegan Version: Use vegan butter (or coconut oil or olive oil) instead of regular butter.
Storage:Cool to room temperature and then store roasted squash in an airtight container in the fridge for up to 5 days.
Reheating: You can eat it cold (it's delicious added to a salad), or reheat it in a microwave (if you don't mind that it's not crispy), air fryer (at 375F for about 5 minutes), or oven (at 350F for 10 to 15 minutes).