In Biggles Takes a Hand, Frau Roth was the wife of Oberst Hans Roth, one time Underminister for Defence of East Germany. Just before the events in the book, Hans Roth, knowing that he had comes under suspicion for harbouring pro-western sympathies, began planning to flee to the West with his family but he was arrested and executed before he had a chance to do so. He had however prepared his family for this contingency and Frau Roth and her two children Moritz and Roth escaped from their house by climbing a rope from a window of a bedroom at the back of their house and made their way into West Berlin. There they stayed one night with a friend Max Lowenhardt, whose daughter, Anna was engaged to Moritz. Anna had worked in England a few years before as a governess and stayed with one Dr Bruno Jacobs, a emigre German dentist. She gave the Roths a letter of introduction to Dr Jacobs, who lived in Hampstead.
Arriving in London, Frau Roth and her family found that Dr Jacobs had moved and the current owner of the house in Hampstead, Mrs Smith did not know where he had gone, nor did Mr Carson, who handled the sale of the property. Frau Roth's problems were compounded because Oberst Hans had given Moritz some secret documents. He had hoped that this would persuade the East German authorities to leave his wifre and children alone. It had the opposite effect, in that a gang of professional assassins led by Ludwig Karkoff was sent on their trail in order to retrieve the incriminating papers.
All ended well for Frau Roth, however. Running short of money, she had gone to a police station hoping to get some information about where Dr Jacobs had gone. Fortunately for her and her family, Chief Superintendent Lowe of the Hampstead police had, by this time, been put wise by Biggles about the doings of Karkoff and his gang. He put the Roths under police protection under Biggles could take over.
The Roths finally emigrated to the United States. Moritz's papers, the source of so much mischief, were handed to the British government. The Lowenhardts later joined the Roths across the Atlantic and Moritz and Anna were married.
Despite their pivotal role in the plot, none of the Roth's actually had a speaking part. Biggles only met them at the end of the story.