Rose is a humanizing influence on the Doctor, really...not his conscience, usually (though she can be, such as in "Dalek") but she does ground him. She gives him a human connection; he has trouble relating to humans at all, trouble even explaining things in a way a normal person can understand (especially when he's been alone for a while, judging by what you see of him after he's been by himself; look at how wacked he is in the first ep!)...but you really find her callous? The Doctor can be, but I never would describe Rose like that; she's so emotional, passionate about so many things. Again, I might be thinking of 2nd season too much...there's many times she's sympathetic to people, maybe I've forgotten all the times she's not. She does handle death of people around her awfully well, but that's a quirk of the show; and also a strength as much as a weakness, because if she were paralyzed by grief or fear she wouldn't be much good in a lot of situations.