Yes, roleplaying games are different in structure than other forms of fiction, and the needs of the story, the people telling the story, and the audience are all unique. They’re still stories, and embracing theme is a relatively easy way to make those stories better. It’s infinitely more interesting when the character kills the monster, steals the treasure, and levels up for some actual purpose — just look at nearly any fantasy novel or movie. Punching supervillains and overthrowing galactic overlords is a lot more fun when there’s some emotional connection to be made, something that people can relate to beyond the fight scenes and explosions.
Theme is Not the Premise
A story’s premise is the heart of what happens during the story, but on a very superficial level. The protagonist overcomes a series of obstacles, usually put in place by an antagonist, to achieve the story goal; that’s the premise. The player characters kill monsters in order to gain treasure and level up. The boy does what heed needs to do to be with the girl he loves, in spite of the people trying to keep them apart. A hero goes on a quest, survives the hazards of travel, and returns home with the prize he was seeking. Those premises might be interesting, and help to attract an audience, but it doesn’t convey any sort of profound meaning or emotional connection with that audience.
Theme is Not the Plot
Plot can mean a lot of things, but for our purposes let’s simplify the definition to indicate a type of story that follows a particular structure. The typical story has a beginning, a middle, and an end. A journey plot starts with the reason to travel, with the travel in the middle, and either reaching the destination or getting back home at the end. A rags-to-riches story begins with a protagonist in poverty, has them on a path to prosperity in the middle, and a happy ending where they’re literally or metaphorically rich. A mystery starts with a crime, has an investigation with twists and turns in the middle, and the crime being solved in the end. These structures can be a framework for the theme, familiar elements upon which you can build greater meaning, explore universal issues, and say something significant about the world.
Theme is a Discussion
When developing a story’s theme, you begin with the point that you want to make. It has to be clear in your head what you want to say, and why you want to say it. Then you need to lay out all of the arguments about why you’re right, and the counterargument is wrong. The protagonist can express your point of view, the antagonist the contrary view, and supporting characters other perspectives. All of the other other elements of the story should also point the audience toward accepting your talking points. You need to make the audience care as much about the theme as you do about the characters and the cool fiddly bits of the setting. They need to feel that they have a horse in this race. This leads us to the final point.
Theme is Universal
Theme is what makes your story universal. Every member of the audience, no matter what their age, life experience, or background, should be able to relate to what is happening in the story on some level. The purpose of theme is to help the audience — the reader, player, viewer, whatever — relate to the elements of the story on a personal level. The circumstances of the story, in terms of genre, time, and place, may not be elements that the audience can relate to, but the have an emotional integrity, a human core, that resonates with everyone.