1. Preheat oven to 400 degrees. Set a large pot of salted water to boil. On a rimmed baking sheet, toss cauliflower sprinkled with turmeric, onion and carrots with 3 tablespoons oil; season with salt and pepper. (vegetables need to be in a single layer, so use more than one baking dish if need be. Roast on lower rack until lightly browned and tender, approximately 20 minutes, tossing once.
Cook pasta in boiling water for 3 minutes. Reserve 1/2 cup pasta water; drain pasta and toss with the vegetables in the roasting pan to get all the yummy flavors. Add the reserved water, too.
In a serving dish toss with Parmesan, parsley, salt, pepper and desired garnishes: toasted walnuts, pinenuts, toasted bread crumbs or lemon juice.