Preheat the oven to 425 degrees F. Cut the butternut squash in half, lengthwise. Cut off the circular orb sections (the end with the seedpod) and save for future use.
Peel the long sections of the butternut squash, then slice them into thin wedges. Core the apple and slice into wedges, unpeeled. Then peel and slice the onion into wedges.
Pile the butternut squash, apples, and onions on a large rimmed 18x13-inch “half sheet” baking pan. Drizzle olive oil over the top and toss to coat. Then spread the squash, apples, and onions out into a single layer. Sprinkle with allspice, salt, and pepper.
Roast in the oven for 15 minutes. Meanwhile, cut the chicken sausages on the bias, into 1/2-inch slices.
Flip the veggies, and spread them back out. Make room on the baking sheet to add the sausages. Place the sheet back in the oven for 10-15 minutes, until the sausages are sizzling. Serve warm!
Keep leftovers stored in an airtight container for up to 3-4 days in the refrigerator, or up to 1 month in the freezer.