Why do people play roleplaying games? To have fun? to hang out with friends? Those are both good reasons, but please let me share another good reason: to improve one's creative abilities. Roleplaying can be a good opportunity to try writing as a group and help each other learn to write better. When the GM leads an RPG session and the players all contribute by playing their characters, everyone can learn something about writing. If someone did a great job of writing a backstory for his or her character and he or she shares that backstory, the other players get a lesson in writing effective backstories. If one player does a great job of portraying his or her character's personality, the other players get a lesson in personality portrayal. If one player does a great job of vividly describing his or her character's powers, the other players get a lesson in vivid description. If the players work together, the whole group gets a lesson in teamwork (which is useful not only when writing and roleplaying, but many other times as well.) If the GM helps players with all of these aspects of roleplaying, then the GM and the players all get useful lessons.
To sum things up, when you really make roleplaying a team activity, you can make it a chance for everyone in the group to learn more about creativity from each other.
I should mention that I couldn't have discovered my own creativity without the help of someone who enabled me to discover it through roleplaying. When this person was the GM for an RPG and he helped me create the deepest character I had ever played, he opened up whole new imaginary worlds to me. Without the things he taught me, Dream Fathom would never have been put together. Thank you, you know who you are!