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. During his BLM career and during his retirement, Rosentreter collected more than 19,000 specimens, the vast majority being lichens, and donated duplicates of the specimens to
herbaria all over the world. He is a leading expert on Idaho's rare plant species and has made a particular effort to protect the species
Lewisia sacajaweana. He is the author or co-author of nearly 100 scientific publications. In 2022 he edited the
exsiccata Anderson & Shushan Lichens of Western North America. He has done considerable research in
grass ecology,
cheatgrass control, and
firewise landscaping and planning. An avid kayaker and naturalist, Rosentreter has participated in efforts to remove trash from the Boise River and its beaches. In 2006 he received the Idaho Weed Hall of Fame Award from the Idaho Noxious Weed Control Association. ==Selected publications==