Once you've gained your independence, it's quite hard to be under the rules of your parents again. But then sometimes you just have to make the most of what life throws at you. For instance, losing a job could mean you can no longer afford the rent you are sharing with your roommate. And the best thing that could save you at the moment is moving back to you parents' home.
If you decide to move back, make sure that you discuss your plans with your parents first. After all, they are used to not having you around anymore. While they may love you just as much as before, they would have to make adjustments because of your move. And it's still their house. While doing so make sure that you discuss how you are going to contribute in the household expenses. If you cannot afford to chip in financially then you would have to offer to help do the chores at home instead. That is fine as long as everybody is clear about what to expect.
Again, it is your parents' house so you would have to abide by their rules. It would be better to do so to avoid conflicts. Make your move is least inconvenient to everyone. You should make sure you're not messy for instance. Instead you should help keep the order at home when you can. Be sensitive to small things such as not blocking the driveway or not making too much noise in the house.