Preheat your oven to 375. Split your squash in half with a heavy knife, and scoop out the seeds (you can reserve them to roast as well if you like). Rub oil on the cut surface and place cut-side down on a rimmed baking sheet. Bake for 20-40 minutes, or until a fork easily pierces the thickest part of the flesh. (We recommend roasting a head of garlic at the same time - just pull off the loose papery bits, drizzle a little oil over it, and wrap it up in tinfoil. Roasted garlic makes everything better.)
If the squash is particularly big and hard to cut, you can even roast it whole, pricked with a fork in several places; it will take a little longer and the seeds are harder to remove, but it's better than chopping a thumb off!
Once cooked, the squash can be scooped out of the shell and mashed with butter or olive oil, maple syrup, and cinnamon. Enjoy!