InVinoVeritas
Adventurer
BLAST!
Did you give me a good reason to own this film?
Rent it first.
Basically, the director's commentary is mostly Courtney Solomon and Justin Whalin totally geeking out over how cool everything is. However, every so often, Dave Arneson pops in to explain what the D&D game is and how certain mechanics work. It's sufficiently a non-sequitur to the rest of the movie that it's a little strange to experience, but yeah, it is indeed his voice.