His early research at Exeter concerned Conduction Electron Spin resonance and spin waves in the alkali metals as well as studies of electron surface scattering in thin metal films. Since being at Exeter he has worked on the optical properties of liquid crystals; explored the interaction of light with structured metal surfaces (plasmonics); pioneered work on molecular rectification and elucidated the fascinating photonic structures in butterfly wings. Over the last two decades he has turned his attention to the exciting area of metamaterials, first at microwave frequencies and more recently acoustics both in air and under water.

Since 2000 he has held several significant positions with regard to UK science. He was Chair of the British Liquid Crystal Society, 2000-2003; Member of the Government Defence Science Advisory Committee from 2005 to 2011; and a Council member of the Engineering and Physical Sciences Research Council from 2008 to 2014. Roy has supervised over 100 PhD students, published over 560 scientific papers in international journals and has more than 20 patents. He has also delivered many demonstration lectures on the wonders of light and colour as well as the mystery of quantum mechanical wave-particle duality to audiences from junior school through to the University of the Third Age.

Although Emeritus he still currently supervises 7 PhD students exploring metasurfaces and maintains links with collaborators at Atlas, Dstl, Leonardo, QinetiQ, Thales and TWI.