I had been writing for years before I picked up the hobby of role-playing games, and then only because I had nothing better to do that night. What I found in that crowded basement was a tight-knit group of friends, and many opportunities to find my voice as a writer.
While the worlds in a role-playing game are usually premade, the characters are not, and there's a lot of space within that world to explore and make things up as you go along. One cannot easily rely on role-playing, or the running thereof, to teach one plotting, however. There's an adage in role-playing: "No plot survives contact with the players." The harder a GM (gamemaster) tries to push the characters toward the predestined plot, the harder they'll push back, and wander off in their own direction, or spot something shiny that has nothing to do with the plot all nicely prepared in advance.
This is excellent preparation for a pantster in training. Many writers complain about characters taking over, wandering off, having personalities of their own. Good characters are like that, and nothing prepares one better than to have real people behind those characters, driving their motivations. A good GM will let the characters run around and explore and be willing to toss out the hours of preparation. An excellent GM will be able to nudge them back toward some semblance of the plot, while still allowing the characters' actions to affect the outcome.
Role-playing has helped in more subtle ways, too, though. Every time I build a new character with a fully fleshed background and motivations, I'm preparing myself to form someone who'll live and breathe on the page. Every time I'm mentally rehearsing my character's motivations and reactions, I'm getting into the head of someone else who can, potentially, carry a story all on her own. Every time I build an elaborate back story that never sees light of day within the campaign, I'm seeing how little of a character's background makes it into the story. Every last word of a character's back story may well be essential, but none of it is blatantly stated for the reader or to people that character meets. I need to know it like the back of my hand, but the reader only needs to know what comes up in the story.
Building characters also helps in another way: the most interesting characters I've played are the flawed ones. I have a lot more fun with idiosyncrasies and quirks than I do with a character's powers or abilities. It didn't take much of a logical leap to determine that the characters people might most like to read about are the ones who are a far cry from perfect.
The most blatant way role-playing has helped me with my writing is that I was able to create a world all my own, and to explore it with my small role-playing group to find the story potential. I haven't written the Via saga yet; it requires a far more skilled approach than I'm capable of, as yet, and I'm still working on the characters who populate it. But I do look forward to the day I can put that story to words, and, hopefully, let people read it.
Do you have any unusual hobbies that have helped you enrich your writing? How have they helped?