As Sammy's best friend, the two share a love for science fiction, which Sammy's parents disapprove of. While working together on an English project, Roxanne suggests they do it on Hedge House, Middletown's rumored haunted house. While Sammy brushes off the idea, Roxanne is persistent, and he eventually agrees.
When Sammy finds himself tormented by an invisible boy named Brent Green, he tries to tell those around him, including Roxanne. However, she doesn't believe him, and even spreads Sammy's story around the school, causing his classmates to ridicule him.
Later, Roxanne and Sammy enter Hedge House, hoping to prove the ghost stories are true. Roxanne seems to get her wish when a ghost approaches and attacks the two, causing them to run off in fear.
Sammy eventually discovers the ghost was actually Brent pulling a joke, but Roxanne never does. However, she does found out that Brent is not only real, but also a human, which are seen as an endangered species.
Sammy describes Roxanne as being very competitive, which often leads to a friendly rivalry between the two. She likes to think that she is the best at everything, and never seems to ask for help. Roxanne seems to be easy to anger and can be very bossy to Sammy.
While no description is given to Roxanne in the book, it is likely she looks similar to Sammy, who is described at the end as an alien with multiple eyes, arms, and heads.
In the episode, she is portrayed as a normal looking girl with brown hair.