The family emigrated to the United States in 1845, living in Missouri at first, but settling in Quincy, Illinois.

He was one of three curators at the Colorado Historical Society and worked on improving Denver's building code.

The Lewis Department Store, though listed in the National Register, is considered significant for its historic rather than architectural association.

Other National Register-listed Roeschlaub buildings include the Central City Opera House (1878), Trinity United Methodist Church (1888), Corona School (1889), Chamberlin Observatory (1890) at the University of Denver, Cheyenne County Jail (1894) now a museum, the Hover Mansion (Longmont) (1902) and the First Congregational Church (Manitou Springs) (1882).

He was the subject of the book Robert S. Roeschlaub: Architect of the Emerging West, 1843-1923 by Francine Haber, Kenneth R. Fuller, and David N. Wetzel, originally published in April 1988 by the Colorado Historical Society and republished by the University Press of Colorado in July 1992.