I just assumed Roguelike fans were well versed in classic gaming. Early RPG's like Dragon Warrior, action/quest games like Zelda, Early Editions of Dungeons and Dragons. Super Mario Brothers 1-3. Arcade classics like Donkey Kong, Galaga...that sort of thing.
EDIT: It will be interesting to see what comes out of the minds of people who lack those reference points. Most the time when I'm thinking up a game idea I get stuck at, "How do I make it more like Zelda/Gauntlet/Bubble Bobble."