In a large saucepan, heat the olive oil on medium-high-heat. Add the sausage & cook till it is browned and is cooked through. Put aside.
Drain any grease from the pan & reduce the heat to medium. Melt the butter. Add the garlic for a few minute.
Whisk in the flour and cook for a few minute. Then add the chicken-broth, half and half. Bring to a boil. Reduce heat to simmer. Gradually add the Parmesan cheese and whisk well to combine.
Whisk in the cream-cheese till incorporated. Then add in the tortellini, and the tomatoes. Mix gently till the sauce is well combined.
Allow it to bubble slowly, covered, until cooked through. It usually takes between 4-7 minutes. Add the basil leaves to the pan and stir. If desired, add red pepper flakes.
Turn off the heat. Standing, the sauce will thicken more. Serve!