Cook farfalle for about 12 minutes, following package directions. Add string beans during last 3 minutes of cooking time. Drain and return to pot.
Meanwhile, heat a nonstick skillet over medium heat. Coat with nonstick cooking spray. Add onion and mushrooms; cook 10 minutes, stirring occasionally. Break Neufchatel into pieces and add to skillet, stirring for about 1 minute until it starts to melt.
Add milk, salt, garlic powder and pepper to skillet. Simmer on medium-low heat for 2 minutes. Add roasted peppers to sauce; toss sauce with pasta. Stir in 1/2 cup of the Parmesan.
Spoon pasta into a large bowl; garnish with remaining 1/4 cup Parmesan and the basil.