Preheat the oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
In a large bowl, toss the chopped pumpkin with olive oil, nutmeg, allspice, cinnamon, chili powder, garlic powder, onion powder, salt, and black pepper until well-coated.
Spread the seasoned pumpkin cubes in a single layer on the prepared baking sheet. Roast for 25-30 minutes, stirring halfway through, until the pumpkin is tender and caramelized around the edges. Serve warm.