Preheat oven to 375˚F. Line a sheet pan with foil or parchment paper and set aside.
Cut squash in half lengthwise and scrape out seeds.
Drizzle each cut side with 1 Tbsp. olive oil and sprinkle with salt and black pepper. Place the squash cut-side down on lined sheet pan, and roast for about 45 minutes or until the skin pierces easily and flesh is very soft. Remove from oven.
Carefully remove hot flesh from skin and place in a medium mixing bowl. Add about 2 Tbsp. olive oil and sprinkle with salt and pepper. Mash with a fork or potato masher until smooth.
Add mashed potatoes to mashed squash and fold together until mixture looks “marbled.”