Character Analysis
Poor Rose is misunderstood and (quite frankly) underestimated by everyone close to her. When we first meet her, Rose has an unnamed mental delay that causes her to act childishly while also being hyperaware and very good with art and colors. Someone pretty evil (cough… cough… Stepmother) has convinced Briony that this is all her fault. Gee, thanks.
Because of their situation—no mother, an overwhelmed father, and an evil dead stepmother—Briony is unable to see Rose for who she really is. She is unable to love her as a friend or twin sister truly might, and instead Briony overlooks Rose, tolerating her—and even despising her at times—all while taking care of her constantly.
Soul Sucker
I've looked after Rose for years and years, and she drained me dry long ago. What's she feeding off now, I wonder. My soul juice? (2.63)
Yikes, right? When Briony says this, we feel a little bad for her—and it certainly seems that Briony feels bad for herself. But what about Rose? How about a little sympathy for the girl who loves her sister and tries her best? She may be a little quirky, but poor Rose is constantly ignored by everyone who claims to love her. Rose deals with all of this with a surprising amount of grace—that is, when she's not screaming or hiding under the table.
Hidden Talents
Throughout the story, Rose's strengths and talents are mentioned in passing. We have to assume that Rose is her own person, though Briony consistently overlooks her. As Eldric notes at one point, "'You have quite an eye for color […] The ribbon exactly matches your sash'" (13.33). Rose's "eye for color" that Eldric recognizes here is not only artistic talent, but also something that makes Rose unique from her sister.
Though near strangers—like Eldric—see her talents, Briony is too busy thinking of Rose as a burden to notice. At one point she says:
Rose has such very peculiar theories on the passing of time. I mustn't listen to the chiming of midday or midnight, I have no birthday. When I ask why, she says it's a secret. (8.115)
While Briony dismisses her sister at various points, this refusal to pay attention to Rose's "peculiar theories" comes at a very real cost to Briony herself. Rose knows about Briony and Stepmother the whole time, and when Briony (and as such, we as readers) finally understand this, we see that Rose's wisdom—like her talents—have been hiding in plain sight this whole time.
Rose the Determined
No matter how many times Briony fails to listen as her sister tries to show her the truth about their stepmother's lies, Rose doesn't give up—she simply continues making collages, mixing profound observations with notes about the colors of things, and hanging out with the sister she loves. Talk about steadfast.
Finally, when Briony is on trial, Robert helps Rose speak up for her sister and prove that she has more to offer than collages and tantrums:
"Robert says I may tell a secret if it's a bad secret," says Rose. "I know it's bad because it keeps Briony thinking bad thoughts." (31.167)
She may be a bit eccentric, but this moment proves to everyone that Rose is a loving and thoughtful person who is worth paying attention to. Her communication methods are a little unusual, but this is a girl with important things to say.