[1] Immediately upon graduating with his PhD in 1971, he became an instructor in the Division of Geological and Planetary Sciences at Caltech and was soon thereafter appointed assistant professor of Mineralogy and Chemistry.

[2] At Caltech, Rossman regularly teaches the introductory mineralogy course, a course in mineral spectroscopy, and a course in oral presentation.

He supervises the optical mineralogy course, co-teaches analytical methods in Geochemistry, and presents guest lectures in Advanced Inorganic Chemistry.

Paul Asimow, describing Rossman's work, wrote, "Within the general rubric of mineral spectroscopy, Rossman's work can be grouped into three principal categories: the origin of color, the effects of natural and artificial radiation damage, and the concentration and crystal chemistry of hydrogen in minerals both hydrous and nominally anhydrous.

"[4] Rossman is author or co-author of more than 380 articles on mineralogy, inorganic chemistry, gemology, and materials science.