In my mind- and I'm not saying this is any more valid than other interpretations, i just say it to offer a perspective- the defining trait of a Roguelike is a top-down perspective in which things are represented with a combination of colour and abstract ASCII-or-similar symbols. I guess DF has, by its very existence, caused me to distinguish between (what I see as) "the Roguelike genre" and "Games that closely resemble Rogue".
- It does also have randomness, richness and permadeath, naturally.
- I believe unidentified objects is taken straight out of D&D. I think of it more as extremely common because of that than a defining feature.
- There are roguelikes out there that don't have "Dungeons" per se- there are Mecha roguelikes, space roguelikes, even a DOOM Roguelike. So if you mean literal fantasy dungeons, no, but if by "dungeon crawl" you mean in the general RPG sense of "venture into an enclosed, danger-filled space to acheive goals and find things of value", no, not so much of that, although I think there might be one or two Roguelike that don't have that.
I dunno, its an interesting question. Some of the greatest games out there, like DOOM or Civilisation, define a genre. Others, like Dungeon Keeper, acheive greatness by smashing our ideas of a genre into little pieces (although it's interesting to note that the former kind tend to come early in that genre's development, and many of their taken-for-granted features were actually quite original when they were released). So I would say that DF *is* a Roguelike... in the same sense that Dungeon Keeper is a real-time strategy, and an action game and a sim. Being Roguelike is part of what it is but doesn't wholly define it. It may be the start of a new Genre.