When a dish will be frozen and then heated again in the oven, you don't want your pasta to be overcooked and mushy by the time it's ready to eat.
When you first cook the pasta, boil it for about half the time recommended on the box, or about 7 minutes or so. Then drain the pasta and run it under cold water. This will stop the cooking process.
Don't worry! The pasta will absorb some of the moisture from the dish and finish cooking when you reheat it.