Professor Robertson was Dean of the Faculty of Natural and Agricultural Sciences and then Pro Vice-Chancellor (Research) at UWA. Since retiring in mid 2013, he has joined the School of Plant Biology as an Emeritus Professor.

His research interests include Plant-animal interactions and their effects on ecosystem processes in marine habitats and the responses of river and floodplain ecosystems to multiple changes, including flow, invasive biota, clearing for agriculture and grazing by livestock.