Set a salted pot of water to boil. Add penne and cook according to directions on package. Drain and set aside.
Meanwhile, set a medium nonstick pan over medium-high heat. Add sausage, break up into small chunks with a wooden spoon, and cook until browned, 6-7 minutes. Remove from heat and drain grease, if necessary.
In a large bowl, combine cooked sausage with ricotta, garlic, basil, red pepper flakes, salt, pepper and 1 1/2 cups of the pasta sauce. Add cooked pasta to large bowl and toss gently to coat.
Coat bottom of a large baking dish with 1/2 cup pasta sauce. Add pasta mixture into dish and spread out evenly. Spoon remaining sauce over top and sprinkle with mozzarella. Bake until golden brown and hot throughout, about 30 minutes.