Preheat the oven to 400°F
Wash the butternut squash
Cut off the stem and bottom
Peel the squash
Slice the squash in half lengthwise
Scoop out the seeds
Cut the squash into cubes or leave halves whole
Toss with oil, salt, and pepper if desired
Spread on a baking sheet in a single layer
Roast for 25 to 35 minutes for cubes
Roast for 45 to 60 minutes for halves
Flip halfway through cooking
Cook until fork-tender
Remove from the oven
Let cool slightly before serving