[Spoiler alert! Don't say we didn't warn you.]
Rosie is good-natured and lovable. She's loyal, intelligent, and sweet. All in all, she's pretty normal: she doesn't understand English that well, having been brought up with the Polish language; she loves snacks like popcorn, is good with children, and is really fond of lemonade and gin; she's good to her friends and holds a serious grudge against her enemies; she patiently endures a series of hard knocks and isn't afraid to stand up for herself in the end.
Just one problem: she brutally murders a guy. What are we supposed to make of that?
During the scene when all the animals go crazy, Rosie uses the opportunity to take revenge on August for the way he's treated her. As Jacob describes it in the Prologue, "She reached for something. A giraffe passed between us – Its long neck bobbing gracefully even in panic – and when it was gone I saw that she'd picked up an iron stake. She held it loosely, resting its end on the hard dirt. She looked at me again, bemused. Then her gaze shifted to the back of his bare head" (Prologue 33). You can just imagine the rest (or read it at the end of the book!).
(This moment is also important in terms of the way the narrative is set up. The Prologue is ambivalent about who killed August. In this passage, Jacob is talking about a female, but he never specifies who it is – it could be either Marlena or Rosie. It's not until the end of the book that we find out the "she" at this important moment is Rosie.)
So, how are we supposed to feel about this? We love Rosie so much, that seeing her turn into a monster is pretty unsettling. Does this remind you of Jacob's violent outbursts? Does your opinion of Rosie change after this revelation? Or do you still love her just the same?
There's one thing that makes Rosie very different from all the other characters in the book: she's an elephant. Yep. Re-read the first part of this character analysis and you'll see that she's pretty indistinguishable from a human: she has very human qualities, like, you know, a personality and a desire for revenge. She's an individual, with thoughts, feelings, and desires. She deserves good treatment as much as the next person – er, elephant. Sadly, like a lot of other characters in this book, it takes her a while to start getting that good treatment.
But even though Rosie's an elephant, Jacob falls for her in much the same way he falls for Marlena (minus the lust part). He frequently lumps Rosie and Marlena together, like when he says "I hate that I've let them [Marlena and Rosie] both down" (12.154). Both are females he cares about, and both are technically in August's domain: Marlena because she's married to him, and Rosie because she's one of the animals he trains. Both Marlena and Rosie seem to like Jacob better, and it's pretty clear that Jacob treats both of them far better than August ever will. Yet, at least for the first half of the book, they're both subject to August's whims.
At one point Jacob questions Rosie's intelligence, saying "I don't know if the elephant is smart enough to connect me to her punishment [which comes from August] and wonder why I didn't do anything to stop it, but I am and I do" (12.154). But Jacob is proven majorly wrong. It turns out that Rosie is quite intelligent: she does understand who's cruel to her and she knows how to take care of herself. Not only does she take revenge on August, she also plays dumb so that the circus scavengers won't take her away from Jacob.
Rosie is just as much a character as anyone else in this book and just like the rest of them she's complicated as heck.