Boil the tortellini: Bring a large pot of salted water to a boil.
Cook tortellini according to package directions until just tender. Reserve 1/2 cup of pasta water, then drain and set aside.
Brown the sausage: Heat a large skillet over medium-high. Add a drizzle of olive oil and the sausage.
Break it up with a spatula and cook until browned and cooked through, 6–8 minutes. Transfer to a plate, leaving some fat in the pan.
Soften the aromatics: Reduce heat to medium. Add onion and a pinch of salt.
Cook, stirring, until translucent, 3–4 minutes. Add garlic and cook 30–60 seconds until fragrant.
Build the base: Stir in tomato paste and cook 1–2 minutes to caramelize slightly. This deepens the flavor and gives the sauce a warm color.
Deglaze and simmer: Pour in chicken broth, scraping up browned bits.
Stir in roasted red peppers and bring to a gentle simmer for 2–3 minutes.
Make it creamy: Lower the heat and add heavy cream. Stir until smooth. Return the sausage to the pan.
Let it bubble gently for 2–3 minutes to thicken slightly.
Season: Add a pinch of red pepper flakes if you like heat. Taste and season with salt and black pepper. Stir in Parmesan until melted and glossy.
Combine: Add the cooked tortellini to the sauce and toss gently to coat.
If the sauce seems too thick, splash in reserved pasta water, a little at a time, until silky.
Finish: Turn off the heat. Stir in chopped basil or parsley and a light squeeze of lemon to brighten everything up.
Serve: Plate with extra Parmesan and black pepper on top. Add more herbs if you’d like.