Toss cauliflower and mushrooms in the oil, thyme, salt and pepper. Place in a single layer on a baking sheet and cook until they begin to caramelize, 20-30 minutes. Stir vegetables halfway through roasting time.
While vegetables are roasting, cook the quinoa. Bring water and quinoa to a boil, reduce heat and simmer, covered until the quinoa is tender and has absorbed the water, 15-20 minutes. Remove from heat and allow to sit for 5 more minutes, covered.
Toss vegetables and quinoa with your favorite balsamic vinaigrette. Garnish with toasted walnuts, additional thyme and cheese. Serve over mixed salad greens. Enjoy!