Can I freeze ravioli filled with goat cheese and caramelized onion, even when the package advises not to? 
It's not going to make it dangerous if you're sensible.  The texture might suffer a bit, but it will still be edible - better than wasting it.  Defrost in the fridge before cooking, not at room temperature.  I have frozen similar products in the past, and honestly don't think they deteriorated at all - certainly less than overcooking. Mostly when manufacturers say products aren't suitable for freezing, they're worried about 2 things:  trying to cook something (probably raw) from frozen that will seem done when it's not, and risking food poisoning.  Defrosting before cooking, under safe conditions, solves that. the quality suffering, and customers complaining.  A few foods suffer badly, like cream, but most don't  