Preheat your oven to 400°F, positioning the racks in the upper and lower thirds. Generously grease two baking sheets with nonstick spray.
In a large bowl, place the butternut squash cubes. Drizzle with olive oil and maple syrup, ensuring an even coating. Sprinkle the salt, cinnamon, and black pepper over the top, and toss everything together to combine. Divide the coated squash cubes between the two prepared baking sheets, ensuring they are spread out in a single layer without overlapping. Discard any excess liquid left in the bowl.
Place the baking sheets in the preheated oven, positioning one on the upper rack and the other on the lower. Roast for 15 minutes. Then, remove the sheets, turn the squash cubes with a spatula, and swap the positions of the baking sheets. Continue roasting for another 10 to 15 minutes, or until the squash is tender and caramelized. Once done, remove from the oven and sprinkle the fresh rosemary over the roasted squash. Serve immediately while warm.