Rosa Lee Guard was born in Charlottesville, Virginia, in 1882, and was educated in the public schools there. She served as Samuel Gompers' secretary from April 1898 until his death on December 13, 1924. Guard often took responsibility for answering correspondence and for routine matters when Gompers was absent on official American Federation of Labor business. When Gompers' eyesight became seriously impaired during the later years of his life, Guard read to him at the American Federation of Labor office in Washington and while he was traveling. Gompers would dictate comments about the readings for Guard to record in a notebook. When Bright's disease affected his heart, she ensured that Gompers remembered to take his medicine on time. Gompers left his personal and unofficial files in the custody of R. Lee Guard, his confidential secretary, and Florence Thorne, his assistant in the writing of his autobiography. Guard mentions a letter written in November or December 1923 from Samuel Gompers to her personally, which she held in her possession, authorizing Guard and Thorne "to go through his desk and his papers." After the death of Samuel Gompers, Guard and Thorne arranged to send the pamphlets written by Gompers to the New York Public Library. After 1924, Guard became chief clerk for the AFL under Gompers' successor, William Green, until her death on May 9, 1937. Guard's creed: "A secretary should be self-effacing, merely a machine for turning out work," was included in her obituary notice.
During her personal time, Guard wrote poetry, entertaining memos and a pamphlet. Some of her writings were published in union publications, but most of her poetry remained outside the public domain.