1) Bring a large pot of water to a boil. Add pasta and cook to al dente. Drain and reserve about 2 cups of the pasta water, and return the drained pasta to the cooking pot; cover with the lid to keep it warm.
2) While the water is coming to a boil and the pasta is cooking, make the sauce. Heat a deep skillet, oiled with the olive oil or sprayed with the olive oil mister, over medium heat. Add the garlic and cook for 1 to 2 minutes, and then add the onions and cook for about 5 more minutes.
3) While the onion cooks, break up the cauliflower to about half-floret size pieces. Put the cooked onion and garlic mixture in a blender to hold. Add the cauliflower to the skillet, along with the stock and the rosemary leaves (no need to cut). Cover the skillet and cook over medium high for 5 minutes until tender but firm.
4) Add contents of the skillet to the blender containing the onion mixture. Add 1/1/4 cups of the reserved pasta cooking water to the blender. Add a pinch of cayenne pepper. Carefully blenderize the contents on a slow setting at first with a towel over the lid, since it is hot and it could spray everywhere. Blend until completely smooth. Use extra reserved pasta water to thin if necessary; otherwise discard the excess.
5) Add freshly grated cheese and cauliflower sauce to the warm reserved pasta in the pot and toss to combine. Add vegetables or fresh baby spinach as desired. Season with salt and pepper to taste if needed. Top with freshly grated Romano cheese and serve hot.