dogeddie: leave the other one to AI.
The AI only determines how a character answers in dual dialogues.
If characters are linked together, they will follow the leader; if not, they will wait until you select them as leader and move them somewhere, etc (you can split up your party to have one walk across town while the another shops, or one steal while the other(s) engage possible witness(es) in conversation to distract them, etc).
There are 4 different companions you can recruit, so you should be able to pick 2 that compliment your main characters and playstyle. Having 2 mages is quite effective, and if you wanted you could also have 2 warriors or archers, as well (though, as with mages, I'd build them a little differently: one two handed and the other sword and shield, or one using a bow and the other a crossbow). I'm not sure how 2 rogues would work, not having played with one.