During her initial nearly two years in Germany, Roper studied with Heiko Oberman at the University of Tübingen, and worked with Ingrid Batori and Hans-Christoph Rublack.

In Living I Was Your Plague, Roper explores some of the more controversial aspects of Martin Luther's personality - his use of vulgar language, his pugilism, and his rampant anti-Semitism.

Roper's Martin Luther: Renegade and Prophet, has been translated into German, Spanish, Polish, Portuguese, Czech and Dutch; in Germany it became a best-seller.

Published to coincide with the 500th anniversary of the posting of the 95 Theses and the start of the Reformation, Roper's biography is one of the first to locate Luther within his social and cultural context, foregrounding his physicality and thus seeking to understand his theology in new ways.

A collection of nine interconnected essays, Oedipus and the Devil explores subjects ranging from the literary culture of the sixteenth century, to early-modern sexual attitudes and ideas regarding femininity and masculinity, to issues surrounding the complex development of marriage, and the use of psychoanalysis in studying witchcraft.

[7] Roper examines why a woman would kill her child, why someone would confess to living with the devil like husband and wife, and why a famous banker might employ a village clairvoyant ('Dorf hellseherin').

Roper's first book questioned the ways in which the Reformation changed gender relations, focussing on the case study of Augsburg, one of the most important cities of the Holy Roman Empire.

Exploring the idea of 'civic righteousness,' Roper argued that the Reformation developed a theology of gender whereby the roles of men and women were clearly distinct within the vision of the 'holy household.'