Ros was a really tricky one for me : I never found myself caring about her. Not just because she wasn't in the books, but the reason she existed, despite not being in the books. She was a plot device in the first series so that we could learn things about the characters that in the book appeared in either the narration or inside the characters' heads. Her being present in Tyrion's introduction and her scenes with Theon, Baelish and Pycelle were there to flesh out those characters, and as such when I looked at her, I never really cared a great deal because she didn't seem real enough to me ; she was just a plot device. When Cersei had her beaten because they didn't want to cast the madam's daughter - logical, because they'd never bothered casting the madam and rewrote the brothel to belong to Baelish instead - plot device, to reduce the casting levels, like making Bronn commander of the City Watch. Every time I looked at Ros, she never mattered to me. However, I was pleased to see that when they elected to kill her they made it a death with purpose ; to underline how dangerous a man Baelish is to cross, and to underline what an irredeemable cunt the King is, as if we didn't already know. For people that haven't been ruined by the book like me, it would have been shocking and poignant. So it's good writing.
Double standards I suppose, when I consider how FUCKED OFF I was when they killed off Irri last year.