Cute and pretty for a twelve year old, she has blonde hair normally straight but presently curled. After being attacked by Eva her right hand and wrist were black and purple with bruises, her upper lip was crusted with blood, and her ear was swollen enough to look like it belonged in a cartoon, puffy and overlarge.
Paige notes she spoiled in a manner different than her step-sister, Ellie Thorburn, while in her timeline Rose Thorburn Junior noted that she made accusations at Callan's girlfriend, who entered her class as a teaching assistant, that ended her career.
Blake realizes as well that she was spoiled rotten by Paul and Jessica, aware that she was pretty and cute, and fully capable of leveraging that to get what she wanted while she still can. She manages to put a lot of bite into very simple criticisms and was an unholy terror in whatever grade she was in and has no respect for Rose and makes that clear in front of everyone.
Blake also suspects she may be a budding sociopath given her behavior and how she views the world in an adult manner while her older brother James didn't, which was why he could see Blake while in a reflection while she couldn't initially. She has very little compunctions about resorting to lethal force and even seems to admire the witch hunters, as well as kill them out of revenge.
Peter points out that she's used to getting her way and doesn't like it when others are superior to her. Once she ends up being cornered she goes for the jugular and starts imitating the most successful person around her, which leads to her emulating Eva later on. She also had a surprising amount of resistance to an attack from a demon of the choir of madness, which is due to her being mentally unwell.
Roxanne only appears at the Hillglades House at the end to try and play up the cute angle to convince her grandmother to leave something behind, but at that point she had already died.
She later appears with the rest of her family after Rose gains the house and comments on how crazy she seems and how they should get the house if that's the case. She is left behind with Ellie Thorburn, Peter Thorburn, and Kathryn Thorburn as well as Callan and Christoff when Rose is taken away. When Peter comes to her about joining forces to get the house to change hands, she agrees since it sounds like more fun when Kathryn tries to stop her since she was in her care at present.
Roxanne reminds her that she excels in hurting people worse than they hurt her or getting in her way and Kathryn agrees not to get in her way as long as she does cause trouble and give up her remote privilages. The house is then attacked by Eva and Andy and she grabs a weapon to stab Andy in the groin, but he was wearing a cup, and Eva kicked her in the face an kept kicking until Andy told her to stop.
When Blake returns she's among the few who can move and believes them to be hit men, admitting she wants to be them and them repay them back by killing them. She helps set up traps, like oil on the steps and knives, and goes into hiding when Eva finds them.
After the house falls under siege by a number of Others and they retreat into the library she remains rather calm until spoken to and asked if she wanted to know anything, the only thing being whether or not practitioners can't lie. When they fall into Limbo she ends up being attacked by ear wigs that she has to constantly dig out of her ears and they eventually start crawling under her skin despite Evan trying to help her, leading to her breaking down and going inside one of the windows and has to be talked out of it by Blake as another Bogeyman appears. He ends up carrying her on his back for the duration of the climb.
Once on top she went to sleep and had a nightmare of the bugs all over her again. When she was woken she lashed out in a panic and pulled out a knife and cut Alexis before they managed to calm her down, lamenting that she'd never be the same again.
Roxanne ends up in the group with Blake and starts lashing out, inadvertently calling out Tiffany on lying. When Blake tells her not to do that she lashes out at him, leading for Peter to call her out on how she's handling the situation where she's not in control and reveals she's armed herself with a number of knives, alcohol, and other things that would be effective in a fight including killing Blake, emulating Eva.
During the Judgement arc, Roxanne was one of the few who weren't heavily affected by the demon attacking them with a maddening scream, with Rose realizing this was because out of all of the Thorburns present, she was the one who was the most unhinged.