Cook pasta according to package directions, adding asparagus, sweet pepper, and squash to pasta the last 3 minutes of cooking. Drain. Return pasta and vegetable mixture to hot saucepan.
Meanwhile, for sauce, in a small saucepan combine Alfredo sauce, the 2 tablespoons tarragon, and crushed red pepper. Cook and stir over medium heat about 5 minutes or until mixture is heated through. Pour sauce over pasta and vegetable mixture; stir gently to coat. If desired, garnish with fresh tarragon. Makes 4 servings.