>How far can I stray from the norm and still consider the game a roguelike?
As much as you want. What makes a good "-like" game and not just yet another boring copy is its originality factor. As in why in some aspects, Quake as a Doom-like succeeded and Half-Life as a Quake-like succeeded.
You have ideas, put them to use, and don't feel shackled down because your starting point was to make a "roguelike" game. Then playtest a lot, you'll see if your ideas work on the field with players.