Cooking cheese tortellini is a really simple process. All you have to do is bring a pot of salted water to a boil, drop in the tortellini, and cook according to the package directions. Mine cook up in about 5-6 minutes. If you're cooking your packaged tortellini for this cheesy tortellini casserole, I recommend undercooking them by just a few minutes. Since they will continue to cook in the sauce once they are baking in the oven, there is no need to have them completely cooked. Once the cheese tortellini is cooked, drain off the water and use your tortellini as desired! It really is that easy!