His research in pharmacology, has been particularly in physiologically based pharmacokinetics (that deals with the movement in time of drugs and their metabolites within the body).

[5] Rowland became a member of the joint Pharmacy-Medicine NIGMS funded program in Clinical Pharmacology, and moved his research from a prevailing descriptive approach to a more mechanistic, physiologically-based one,[6] including the clearance concept[7][8] that helped lay the foundations of modern pharmacokinetics.

In 1975 Rowland returned to the United Kingdom to take up a position of Professor of Pharmacy, University of Manchester where he extended his research on physiologically based pharmacokinetics[10][11] including development of an in silico method for predicting tissue distribution of drugs based on tissue composition and physicochemical properties.

[12] In 1983 he founded Medeval,[13] undertaking early stage clinical evaluation of new medicines under development.

[19] Rowland has published over 270 research articles in international peer-reviewed journals, and over 60 book chapters and conference reports.