1.Bring A Large Pot Of Lightly Salted Water To A Boil; Cook The Rotini At A Boil Until Tender Yet Firm To The Bite, About 8 Minutes; Drain, Reserving 1/2 Cup Cooking Water. 2.Heat A Small Skillet Over Medium-Low Heat. Place Walnuts In The Hot Skillet; Continually Cook And Stir Walnuts Until Toasted And Fragrant, 3 To 5 Minutes. Remove From Heat And Chop Walnuts. 3.Heat Olive Oil In A Pan Over Medium Heat. Cook And Stir Garlic In Hot Oil Until Golden, 2 To 3 Minutes. Remove Garlic From Pan And Set Aside. 4.Cook And Stir Cauliflower And 1/2 Teaspoon Kosher Salt In The Same Pan Over Medium-High Heat, Stirring Occasionally, Until Cauliflower Is Tender, 8 To 10 Minutes. 5.Pour Balsamic Vinegar Over Cauliflower. Cook And Stir Cauliflower Until Balsamic Vinegar Has Reduced, About 1 Minute. 6.Stir Walnuts, Cooked Garlic, Red Pepper Flakes, And Rosemary Into Cauliflower Mixture Until Well Combined. 7.Stir Cooked Rotini And Reserved 1/2 Cup Cooking Water Into Cauliflower Mixture Until Well Blended. Sprinkle 1/2 Teaspoon Kosher Salt And Parmesan Cheese Over Rotini And Cauliflower Mixture.