I'm creating a roguelike definition that is partly an answer to rather poor one they made in International Roguelike Development Conference 2008. Then I heard that Rogue didn't have player classes. At least the original Rogue which I actually had never even played. My only contact to Rogue was in Atari ST era when I played a commercial Rogue published by Epyx. It had graphical tiles and I could swear it was more complex than the original (I guess it's 3.6 from Roguelike Restoration project).
The problem in my definition is that it makes Rogue itself a non-roguelike game, because you can't select a player class. Yeah, it's kind of funny. In my definition Rogue is an adventure game. I had this idea of building the definition on top of role-playing, but it seems that Rogue itself is hitting this definition hard from beyond the grave. My first contact to "roguelikes" was Nethack so it was always my idea of a true roguelike and the foundation of the definition.
The absence of role-playing in Rogue makes it harder to define a roguelike, but maybe it's still possible to create a decent definition including adventure games (simple form of role-playing).