I'm flipping all around in the book and I can't seem to find any discussion on party composition.
It seems as if there is an implied assumption that one player is the Rogue Trader and the rest of the players are the other major "officers" of the ship, somewhat how Ars Magica has one Wizard and the rest are the attendants of the Wizard.
Now part of my confusion I suppose is that the system is still fairly well chained to the old school method of "roll up your character and see what you are going to play." So the system to some degree is pushing people to not even know what they are going to play when they first sit down to make a character.
Thankfully with RT they included the point buy for you stats, which was grievously absent from DH. The character path is also a better system as it is removing a lot of the random tables that determine who you are going to be. I understand some people really enjoy this old school style of character generation, but after 30 years of gaming when I make a character I want it to be exactly what I want it to be. It was dissapointing to see that there are still a frew random tables embedded in the character creation process. Ideally the system should allow players to create characters on their own time, particularly with a system that involves a great deal of hard coded fluff generation along the way.
Anyway, so far in terms of character roles the system seems to be pretty vague. What if several players want to be a Rogue Trader? I know a good GM can put together enough fluff justification for several to be exploring together, either as members of the same family, or allied families, etc. The text is so chocked full of fluff support, but it doesn't seem to address this assumed character hierarchy.