Abundant literature shows that on Western European lowlands, the transition from the Middle Iron Age to the early Roman period involved major changes in livestock practices, with the emergence of specialised and selective animal husbandry. Very little information is available about how the Roman conquest affected mountain livestock practices, despite them being of crucial importance for understanding the integration of mountain regions in the economy of the Roman Empire. To characterise this activity and evaluate its economic importance, we applied a combined archaeozoological and field survey approach to the eastern Pyrenees as a study case. The interrelation of these data was also contextualised with the available palaeoenvironmental record. This interdisciplinary approach allowed us to document an intensive and specialised animal husbandry in the mountains, probably focused on sheep, that would have involved a more intensive use of the highlands and the creation and maintenance of pastoral grasslands. We propose that these changes should be linked to greater pressure on the lowland pastures and an increased demand for wool as a result of the incorporation of eastern Pyrenees into the Roman market economy.