When I was mentoring some young people several decades or so ago, I was intrigued with some RPG games they were playing--now and then they used my computer and my email service. And because they were using my computer and email they left enough evidence behind for me to figure out what games they were playing and how to access them. I actually enjoy many games so I set up my own character in those games mostly in an investigative capacity but occasionally just enjoyed playing them.
Some were absolutely delightful. Yes you were role playing mythical characters in mythical settings and you had to utilize magic and engage in battles and all sorts of things. But just as books and movies that engage in pure fantasy--all normal people of all ages easily separate fantasy from reality in their minds and hearts--are fun, entertaining, and for the most part express and glorify heroism, compassion, innovation, resourcefulness, and triumph of good over evil--I found those games to be harmless, to engage the person to solve puzzles, problems and master skills, etc., and pretty much okay for kids and adults alike.
And some were not that. All manner of vulgar language, immoral sexual encounters, the worst kinds of depraved fantasy and in more than one case moving from the fantasy of the game into a person's real life resulting in adultery, broken homes, dangerous encounters, and certainly unhealthy for all, most especially the young. I eventually, in another capacity, took some on line training to identify, spot, and report adults preying on children and other vulnerable for nefarious purposes in those games. They were absolutely evil.
Needless to say I pulled the plug on those games with those kids I was mentoring and engaged in some serious counseling with them.
I think as Christians we have to be discerning. I cannot find evil in enjoying medieval fantasy or modern fantasy such as Star Wars, Star Trek and such, that teaches concern and caring for others, encourages innovation, courage, inventiveness, imagination, possibilities, wonder, and most importantly the virtues of good over evil and makes it clear which is which.
But we can also recognize that which does not edify, that does encourage people to sin, to engage in activities that are degrading, harmful, destructive, and just plain wrong. And there is definitely RPG that no Christian should endorse or engage in.