Can't, or Won't, Write a Narrative

Chances are you already know how to write a narrative roleplaying scenario.

What is a narrative? "Cass hit Jargo" is a statement; there is action, but no true narrative. A simple narrative needs a description of cause and effect. "Cass hit Jargo, so Jargo him back" has narrative; each element alone is merely statement, but together they start to tell a story, albeit simple. This kind of narrative is already implicit in any roleplaying game. Going from a simple narrative to a simple story is not a difficult leap at all, it merely needs a structure. A beginning, middle and end is the simplest: "Cass hit Jargo, and ran off. Jargo pursued Cass and hit him back" has a structure. Without any particular intent most roleplaying scenarios have a similar structure, the inciting incident at the start that makes the characters undertake whatever the mission, investigation, or journey that the middle of the scenario/story comprises. The resolution of the scenario: finishing the mission, the objective of the investigation discovered, completing the journey, or even failure to do these things marks the end of the story, and is a natural consequence of the first two elements. Building on these elementary premises is something we learn from being read stories as children, it isn’t hard.
Roleplaying systems also intuitively lend themselves to the creation of character motivations, both for player-characters and non-player characters. Such character motivations can be used to create sub-plot and narrative tension within the story structure. If the players begin to see motive for the way the story is turning, they begin to feel a much greater sense of narrative involvement. Detail adds the final flourish.
Using all these elements could transform a simple story, like the interaction between Jargo and Cass, into something more epic: "Cass, the bastard eldest son of the Lord of Toramas beats his brother Jargo senseless, and flees the scene. The following day Jargo hires a group of bounty hunters to search the town for his brother. After some investigation, the bounty hunters learn that Cass left Toramas in the company of a hooded companion, heading for the neighbouring province of Sekris. Jargo accompanies the bounty hunters on the journey across the mountains and corner the fugitive brother in a Sekrisian village inn. Outnumbered, Cass is subdued and bound. Jargo beats his defenceless brother demanding to know the whereabouts of a girl called Lirande, but Cass refuses to tell him". As it is possible to see from the example, the original story kernel is there, but within that we now have character motivations, as well as a developing plot with the Lirande. The story is also leading towards a point where the other characters involved, the bounty hunters, may wish to choose to switch loyalties to Cass, rather than their current employer Jargo (creating a sub-plot). A story will still happen whichever they choice they make, it will just be a different one.
As has been shown, creating a storyline is not difficult, nor is using character motivations to flesh it out. In the example above the narrator is expecting the player-characters to side with one brother or the other, but there is always a possibility that they might do something that wasn’t as predictable. Presumably, he was also banking on the player-characters successfully learning that Cass had fled across the mountains into Sekris in the first place, and that the characters manage to make that journey, but they might not have. Being adaptable and able to re-think a narrative plot-arc on the fly, or between sessions is not that difficult either, but it is the key to being a good narrator. Even if some part of a plot is compromised, a new course for the story will be available, and such dramatic and unexpected turns of events can be one of the great attractions of roleplaying.