Not the author, but if you're confused, I recommend checking out the 2400 Emergency Rules and this blog post. :)
Players can roll various dice - they do so to avoid risks of their chosen actions. d6 by default, higher dice if they have a skill relevant to the action, d4 if hindered, potentially extra dice if being helped - see the Rolling section.
The d6 rolls in Running The Game are meant to be done by the GM.