Bring a large pot of salted water to a boil. Cook pasta to al dente and reserve ¼ cup of the starchy pasta water before draining. Drain the pasta, but do not rinse.
Either heat up leftover pumpkin cheese sauce in the same pot, then add in pasta and toss to coat. You might want to add a bit of pasta water to smooth out the sauce (this is optional). Alternatively, you can add drained pasta to serving bowls and pour heated pumpkin cheese sauce over top. It's a personal preference. Garnish with vegan parmesan, toasted walnuts, fresh sage, and ground black pepper. Serve immediately.