Over the past decades, the disciplinary boundaries between Roman history and archaeology have begun to fade, as archaeological proxy data started playing an important role in studying socioeconomic processes and phenomena. This is especially true for several key debates such as those on Roman economic performance, diet and nutrition, and migration and mobility. More recently, archaeological sciences, such as stable isotope studies, have increasingly started contributing to these debates too. This paper is aimed at reviewing the valuable contributions stable isotope studies can make to these debates from the economic historian’s perspective and focuses on the interpretative side of such studies: what sort of economic meaning is attributed to certain results? It will be ascertained that there sometimes seems to be a divergence between the interpretations made by isotope experts and what many economic historians would conclude. The main cause for this lies in differences in the underlying assumptions as to the working and performance of ancient economies. We will provide examples where the same isotope results can be interpreted completely differently by switching between sets of underlying assumptions. We will argue that greater interaction between economic historians and stable isotope experts is desirable so as to avoid the emergence of parallel debates and to facilitate the construction of stronger, well-integrated narratives.