Is this a typo?
Since the game has textures, and probably music and voice samples.

Remember, this is still an N64 port so the resources had to be loaded in embarrassingly little memory. It's a lot of awesome packed in a tiny package ^_^

You would be surprised how many games from the 90s were much, much smaller than the capacity of the CD they came on. Even though some filled the rest with a CD-audio soundtrack (like Shadows of the Empire), Rogue didn't. So even if you make a disc image of your original dics from 98 with Alcohol or Nero, that won't be much more than 100 MB either.