Preheat oven to 400°.
In a large oven-safe pot, over medium heat, brown the sausage, breaking it up with a wooden spoon. As it's browning, push the sausage to one side of the pan and saute the onion and peppers on the other side at the same time. The sausage may release enough fat to cook the onions and peppers in, if not, at a bit of olive oil. Stir each half occasionally, don't worry if they mix together a bit (about 10 to 15 minutes).
When the sausage is fully cooked and nicely browned (drain the fat if you like) and the veggies softened, mix together, turn off the heat, and add all other ingredients except the fresh mozzarella.
Mix everything together very well. Press the tortellini down into the sauce as best you can to ensure even cooking. Top with the slices of fresh mozzarella (you may not use all of it, depending on how cheesy you like it!).
COVER (either with the pot lid or tin foil), and transfer to the oven. Bake at 400° for 30 minutes.
Remove the cover and pull out a tortellini with a spoon to taste if it is done. Careful, it's hot! If it isn't, cover and cook 5 more minutes, then retest.
When the pasta is cooked through, turn oven to high broil and return the pot uncovered for 3 to 5 minutes until the mozzarella is starting to brown and bubble (keep an eye on it!).
Garnish with fresh chopped basil or parsley and serve.