During her main publication period at the University of Michigan from 1926 to 1937, E. W. Erlanson described 18 new Rosa L. species and varieties (Rosaceae), most from the midwestern United States. The majority were grown and hybridized at the University of Michigan Botanical Garden, where she collected many specimens for the University of Michigan Herbarium (MICH) over a period of years. Some living collections were hers, but most were from others who sent living plants usually without voucher specimens. For this reason and the inability until recently to use sheets as types from living collections under specific circumstances, type selections were at times inappropriate. Nevertheless, seven (almost half) of the cited holotypes here are in MICH, in addition to three lectotypes designated here, as well as isotypes and isolectotypes. A total of 40 taxa with either type data or in synonymy are identified in 10 categories of Rosa species, subspecies, and nothospecies following the Flora of North America treatment. Lectotypes are designated here for the following 19 names: R. acicularioides Schuette, R. acicularis Lindl. var. bourgeauiana Crép., R. arkansana Porter, R. blanda Aiton fo. carpohispida Schuette, R. blanda var. glandulosa Schuette, R. blanda var. hermannii Erlanson, R. blanda var. nuda Schuette, R. blanda var. subgeminata Schuette, R. californica Cham. & Schltdl., R. carolina L. var. aculeata (Schuette) Erlanson, R. carolina var. litoralis Erlanson, R. deamii Erlanson, R. gemella Willd., R. nitida Willd., R. carolina var. inermis Schuette, R. carolina var. sepalorelevata Schuette, R. pensylvanica Michx., R. ×rudiuscula (Greene) Erlanson, and R. suffulta Greene var. valida Erlanson. One neotype is designated, R. palustris. In addition, holotypes of the following taxa are identified for the first time: R. blanda var. setigera Crép., R. blanda var. hispida Farw., and R. blanda fo. alba (Schuette ex Erlanson) Fernald.