Jamie Rossjohn is principally known for his contributions to the understanding of disease and the vertebrate host response, both from the aspect of protective and deleterious immunity. Namely, he has used structural biology to understand how T cell receptors recognise peptides, lipids and metabolites. Specifically, he has unearthed structural mechanisms of Major Histocompatibility Complex (MHC) polymorphism impacting on viral immunity, drug and food hypersensitivities and T cell mediated autoimmunity. Rossjohn has pioneered our molecular understanding of how T cells bind lipid-based antigens presented by the CD1 family. He has elucidated the structural basis of how vitamin B metabolites are presented by the MHC class I related protein, MR1; this revealed an entirely new class of antigen for T cells.

Rossjohn has held a number of full time research-only appointments, including Australian Research Council and National Health and Medical Research Council Fellowships. He is a Fellow of a number of Academies, including Australian Academy of Science, Academy of Medical Sciences (UK and Australia) and the Learned Society of Wales.