Hi Spacediceman
The character roles in Impulse Drive are generally expressed through two different aspects. The first is the most obvious, and is expressed as what they do for their crew as a part of the team - a pilot or face, a detective or tracker, a scientist or doctor, a space wizard, a hardened warrior, etc.
The other aspect is how they interact with the crew - A stoic tough guy, a volatile hothead with a heart of glass, a charming liar, A naive outsider, a shadowy manipulator, a wise figure dispensing advice.
A lot of what made it into an archetype is based on the archetypes we see in popular media. The Scoundrel has a lot of Han Solo in them.