Turn your oven to 400°F and line a baking sheet with parchment paper for easy cleanup.
Peel your butternut squash, scoop out the seeds, and cut into one-inch cubes so everything cooks evenly. Toss the squash with olive oil, salt, and pepper on your prepared baking sheet. Roast for 30-35 minutes until tender and golden brown, stirring once halfway through.
Get a big pot of salted water boiling and cook your pasta until it's al dente. Scoop out one cup of pasta water before draining everything and setting pasta aside for now.
Heat the remaining tablespoon of olive oil in a skillet over medium heat until it's nice and hot. Toss in minced garlic and sage leaves, cooking for 2 minutes until everything smells amazing.
Put roasted squash, garlic, sage, broth, nutritional yeast, and nutmeg into your blender together. Blend on high until completely smooth and creamy, stopping to scrape sides if you need to.
Pour that gorgeous butternut sauce over your drained pasta and toss everything together really well.
Splash in some reserved pasta water bit by bit until you get the perfect sauce consistency. Taste it and add more salt, pepper, or nutritional yeast if you think it needs anything.
Top with fresh sage leaves, red pepper flakes, and extra nutritional yeast before serving it up. Serve right away while it's hot for the best flavor and texture.