This is kind of a throwback to Chainmail in the early 1970s and what the players did to change it into the first dedicated roleplaying game. If you have a working knowledge of roleplaying games you can introduce new players to the tabletop RPG through any tabletop wargame. All you need to do is take a profile of a character from, say, WH40K and add a couple of stats for social interaction. Stick on a 'Charisma' stat or a 'Social Skills' stat and you've got a character to play. The stat can be random or whatever and you have to roll the stat or less on a D6 to succeed.
So, next time you're wargaming with try suggesting adding the stat and try roleplaying out a parley between the two sides and take it from there. Or try a basic dungeon bash - set up some combat in catacombs and send in several players with defined characters. Set it up as a basic skirmish but suggest they talk in character when discussing tactics or sharing info. Maybe even throw in a couple of NPC-types and roleplay them yourself, kind of lead the way and show how it's done.
You never know, they might go for it and expand on the characters using the wargame. From there you can introduce them to RPGs. Even wargamers who had no interest in RPGs might go for that and, at the very least, do the roleplaying as an extension of the game.
Either way, any wargame can be used as a rudimentary tabletop RPG.