 He was a Nebraska delegate to the 1908 Republican National Convention and a member of Republican National Committee, 1908–12, serving as its chairman in 1912 and planning its convention that year.Rosewater later moved to Philadelphia, Pennsylvania, where he became involved in planning the Sesquicentennial Exposition, which celebrated the 150th anniversary of the signing of the Declaration of Independence.He continued his newspaper career writing columns for various papers and wrote an unpublished biography on his father.