I'm going to wake my roommate up to take care of her dog
Why do you think you need to do that?
I'm not going to take care of her dog, its her's not mine.
It is wrong to let a pet suffer if they have to go potty. You can let the dog out on your own and bring it back in real quick when it is done.
Are you an animal rights activist or something? I've seen what they do to people and believe me this dog is in good hands with them.
There is nothing that obligates you to help, but since you are the roommate it would be a common courtesy.