An author of fiction is someone who never gives up playing "make-believe". It is the same with a Role-player. That's why I think that role-playing is a good way to become an author: It stimulates one's imagination, by teaching one how to create situations, characters, even localities.
As a side note, I think it is rather hypocritical for people to encourage their children to live in the "real world, and to give up playing make-believe, then shell out money to buy the make-believe that authors of fiction come up with.
Role-playing is nothing more than "make-believe" on often a grand scale. We create characters, with strengths, weaknesses (or said character will have weaknesses if one wishes to be a good role-player), characteristics, and so forth.
There are many types of role-playing. One most conducive to becoming an author is the PBEM, or Play By E-Mail. Multiple role-players send in e-mails describing their characters actions, thoughts, and speech, which are combined into a master post, which is then sent out to all players according to a certain schedule.
Then there is message board role-playing, which takes place at a slightly faster pace. This role-play simply describes a single situation, such as a conversation or fight. It is good for learning how to react to a situation, while also learning how to describe situations clearly.
Chat room role-playing is much faster paced. It teaches brevity, without which a story or book can quickly become incredibly dull. It does not lend itself very well to descriptiveness, but there are many cases where lengthy descriptions are to a story's detriment.
In-person role-playing (for example, sitting around a table playing Dungeons and Dragons), is not as facilitating to becoming a writer as other methods, as no writing is taking place, and much depends on luck. However, it is good for coming up with ways to deal with unexpected situations, as one's writing may bring one's characters to an unforeseen pass.
However, all types of role-playing teach you to work within a set of rules. If one writes with no rules in mind, then all a story has is unlimited heroes facing unlimited villains, and one is left wondering "What, precisely, was the point?" and the book gathers not creases in the spine and pages, but dust.
Working within a certain set of rules creates adversity, as one must either work within the rules of his/her society or break them somehow. This is what creates interest.
Thus, being a role-player is often a springboard to being an author of fiction, as you learn to create characters and situations, describe their actions, speech, and thought, as well as how they act, speak and think.
After all, role-playing and fiction writing are nothing less than making believe.