Katherine Rochefort, also known as Kay or K, is an investigator for the Seven-O Special Crime Investigation Unit. Her primary focus is investigating cases involving the dangerous drug Anthem within the Double Decker partnership system, working alongside her assigned partner, Deana del Rio.

Katherine operates as a strict by-the-book officer, adhering firmly to rules and procedures. This approach frequently clashes with her partner Deana's independent, protocol-disregarding cowboy cop mentality, creating a defining friction in their professional dynamic during investigations.

Within Seven-O, Katherine is relatively conventional. Her most notable eccentricity is an enthusiastic interest in food, including a notorious sweet tooth and a tendency toward being a big eater. She also possesses an exceptionally low tolerance for alcohol, becoming easily inebriated even by non-alcoholic beer.

She participates in field operations, including undercover work. For instance, she joined detectives Doug Billingham and Kirill Vrubel posing as a reporter to infiltrate a factory connected to Anthem smuggling. Her character design features a signature green color, consistent with Seven-O's color-coding practice.

Variations exist in the spelling of her surname across sources, appearing as both "Roshfall" and "Rochefort".