Display omitted •Real coffee bean motion in a pilot-scale drum roaster was mapped using PEPT.•Coffee bean density, drum rotation speed and batch size determine flow profiles.•Distinct regions of occupancy correspond to beans in-flight and the bean-bed.•Data can be coupled with heat transfer simulations for physics-driven models. Physicochemical transformation of coffee during roasting depends on the applied time–temperature profile (i.e., rate of heat transfer), with heat transfer phenomena governed by particle dynamics. Positron Emission Particle Tracking (PEPT), a non-invasive imaging technique, was used here to characterise the granular flow of coffee in a real, pilot-scale rotating drum roaster. The experimental study established the impact of drum speed, batch size and bean density (i.e., roast degree) on the system’s particle dynamics. Particle motion data revealed two distinct regions: (i) a disperse (low occupancy, high velocity) region of in-flight particles and (ii) a dense (high occupancy, low velocity) bean bed. Implications of these results for heat transfer suggest that controlling drum speed for different density coffees will provide roaster operators with a tool to modulate conductive heat transfer from the heated drum to the bean bed. These comprehensive data thus inform roasting best practices and support the development of physics-driven models coupling heat and mass transfer to particle dynamics.