Cook the tortellini according to package directions.
Meanwhile, heat olive oil in a large skillet over medium heat. Add garlic and cook for 1 minute till fragrant. Add mushrooms, green peppers, salt and cook until tender. Remove from skillet and set aside.
Add butter to skillet, sprinkle flour over the melted butter and stir until a light paste forms.
Gradually whisk in cream until smooth and fully incorporated. Let the sauce simmer for 1-2 minutes to thicken slightly.
Add cooked and drained tortellini, garlic, mushrooms and green peppers to the cream sauce and cook for 2 minutes.
Stir in mozzarella cheese and turn off heat. Taste, add salt if needed. Top with cracked black pepper.