Prepare tortellini according to package directions. Meanwhile, in a large skillet, cook sausage over medium heat until no longer pink, 6-8 minutes, breaking into crumbles; drain. Stir in pasta sauce; heat through.
Drain tortellini, reserving 1 cup cooking water. Add tortellini to sauce and enough reserved cooking water to reach desired consistency; toss to coat. Stir in Parmesan cheese; dollop with mascarpone cheese. Sprinkle with chili flakes if desired.