Rosamond Thoe was born in Devils Lake, North Dakota, on April 26, 1904. She was the daughter of Halvor and Jennie (Sampson) Thoe. Rosamond was educated in Devils Lake and graduated from high school there in 1922. She took a course at Valley City State Teacher's College before marrying Harry O'Brien on December 31, 1923, in Devils Lake. Harry was born and raised in Devils Lake, served in World War I and attended Dunwoody Institute in Minneapolis, studying journalism.

In 1930, Rosamond and Harry purchased the Walsh County Press newspaper, published in Park River. Harry O'Brien was elected to the North Dakota House in 1935, where he served until 1941, when he was elected to the North Dakota Senate. He continued to serve in the Senate until 1952, when he decided not to run for re-election. Rosamond was then elected to fill her husband's former seat. She served the Senate continuously until 1960, when she decided not to seek re-election. Ironically, both of the O'Briens were, for a time, the only Democrats in the Senate.

Harry O'Brien died in 1953, and Rosamond married Kenneth Lowe on April 11, 1959, in Park River. After Harry's death, Rosamond became the sole editor and publisher of the Walsh County Press. She also taught a course in journalism at Walsh County High School, assisted with the publication of the school newspaper, was a member of the North Dakota Press Women and president of the North Dakota Federation of Women's Clubs. She was presented with the Woman of Achievement Award by the North Dakota Press Women in 1960.

Kenneth Lowe died in 1971. Rosamond Lowe died February 6, 1974 in Grand Forks.