Rosentreter graduated in 1974 with B.A. in botany and biology from the University of Montana and in 1976 with M.A. in biology from Clark University. From 1978 to 1977 in Browning, Montana he was a high school science teacher in biology and earth science, as well a cross-country and track coach. From March 1978 to January 2013 he was a U.S. Bureau of Land Management (BLM) employee, based in Boise, Idaho. He worked for the BLM both statewide and regionally, often as an educator. At BLM's Idaho State Office he was the program manager for rare and endangered plants and for weed management. He also assisted on wildlife projects, vegetation mapping, and land restoration. During his BLM career he received in 1984 a Ph.D. in botany from the University of Montana. There he taught courses in plant taxonomy, plant physiology, and agrostology. He was an adjunct professor at several universities, directed independent study in several academic disciplines, and was an occasional substitute professor in general botany, mycology, plant systematics, and mammalogy. Beginning in 1988, he served as a graduate faculty committee member at Boise State University, Idaho State University, Brigham Young University and Utah State University for several M.S. and Ph.D. students. At Boise State University he taught, from 1985 to 1989, flatwater and whitewater canoeing and, from 2001 to 2012, landscaping with native plants. (Pages 14–16 contain a list of Rosentreter's publications from 1973 to 2015.)
