Cook pasta 'al dente' according to package directions.
Meanwhile, heat a large skillet over medium heat. Add sausage and cook, stirring frequently, until browned and cooked through, 5 to 10 minutes. remove sausage from pan. Leave a little fat in pan (for taste).
Add 1/4 cup olive oil and bring heat down to medium-low. Add squash and onion and cook, stirring frequently until soft, about 5 minutes.
Add olives, garlic powder, Italian seasoning, and red pepper flakes; season with salt to taste.
Drain pasta, reserving 1/2 cup cooking water. Add pasta to skillet and toss to combine. If pasta seems dry, add cooking water 1 tbsp at a time, tossing between each addition. Add cooked sausage and combine.
Transfer pasta to a large serving platter, drizzle with olive oil, and sprinkle with parmesan cheese or crushed croutons.