Bring a large stockpot of water to a rolling boil. Add 1 teaspoon salt, cauliflower and broccoli. Cover and return to a boil. Uncover and cook on medium-high until crisp-tender, about 7 minutes. Remove vegetables with a slotted spoon and reserve liquid for cooking linguine.
Heat olive oil and garlic in a skillet. When garlic is lightly browned, stir in mushrooms, salt and dried red pepper. Saute about 6 - 8 minutes.
Stir in broccoli and cauliflower and continue cooking 10 minutes. If it becomes too dry, add some of the reserved liquid. Bring remaining reserved liquid to a rapid boil, adding water if needed and add linguine, stirring with a fork to prevent sticking. Cook about 10-12 minutes. Drain.
Reheat vegetable mixture. Stir in linguine.
Top with cheese mixture. Dust with more grated romano and serve immediately.