Episodes 1 & 2 [re-watch]

[JHyde]

In regards to why it's Ros and not Adam who goes looking for Zaf I think it comes down to a few main things.

Adam is the team leader and is in charge of the main mission of finding the vaccine. Ros is one who comes across the information via the French, so she is the one who has the information that Zaf may not, in fact, be dead. At the end of the double parter Adam is pretty much a wreck so it's not surprising that it is Ros who will go looking. And I agree with the general consensus that Zaf and Ros had built a good relationship on the Grid.