Bring a large pot of salted water to a boil. Add the pasta and cook as the label directs; reserve one cup cooking water, then drain.
Meanwhile, heat one tablespoon olive oil in a large nonstick skillet over medium-high heat. Add the squash, 1/4 teaspoon salt and a few grinds of pepper.
Cook, stirring occasionally, until golden and tender, about five minutes. Transfer to a plate and set aside.
Repeat with the cauliflower
Add the remaining one tablespoon olive oil, the mushrooms, 1/4 teaspoon salt and a few grinds of pepper to the skillet. Cook, stirring occasionally, until lightly browned, about five minutes.
Add the butter , sage garlic, onion and red pepper flakes. Cook, stirring, until the onion softens, about two minutes.
Add the pasta, squash and 1/4cup of the reserved pasta cooking water to the skillet. Cook, stirring, until heated through, one to three minutes.
Stir in the cream and reduce by 1/2 then stir in 1/2 cup parmesan, add some of the remaining cooking water to loosen if desired. season with salt and pepper.