If the dog is yours, then talk to your boy friend, and discuss it with him. If he expects you to take your dog, then you need to take your dog. And then you have to have a conversation with your parents, and possibly set up a temporary kennel for your dog so that when you are not right with him, he is totally separated from your parents' dog or dogs.
So you have to have a plan.
If your boyfriend is fine with keeping the dog temporarily it may be easier on the dog, if you do not move him to your parents, only to move him back out when you get your own place.
Moving back home is not always easy when you have been on your own. Else, we would all be living with our parents forever. Independence is hard to give up. So fewer changes might be better on your dog, as they are creatures of habit, and each change can reek havoc on them.
Why not just get married to your boy friend, kick out the roommate, and live with him and your dog? That seems the easiest route
. Kind of hard on the roommate though.