Rosalee Longmore was born on August 5, 1952 and grew up on a family farm at a time when many communities had their own hospitals, which provided a wide range of services. Her father being chronically ill, the family had to relocate to Saskatoon, where he died waiting for a kidney transplant. It was this experience that caused Longmore to pursue a career in nursing. After graduating from high school in Weyburn, she attended nursing school in Regina and in 1976 graduated as a registered nurse. She became an active member of the Saskatchewan Union of Nurses (SUN) Local 66, where she served as vice-president, president, and member of the negotiating committee.
In 1984, Longmore held her first position on the SUN Board of Directors as the representative for long-term care nurses. She has been on the SUN Board ever since, and became president in May 1998. As SUN president she also serves as vice-president of the Saskatchewan Federation of Labour and on the Executive Board of the Canadian Federation of Nurses. Longmore is also chairperson of the Board of Directors of the Canadian Centre for Policy Alternatives, Saskatchewan Office, a left-wing research and policy think tank; a member of the campaign cabinet of the United Way of Regina; an active member of nursing regulatory agencies and government committees; and an executive member of the Regina Figure Skating Club and the Queen City Soccer Association.
One of the highlights of her career was in 1999, when she led 8,400 registered nurses and psychiatric nurses on strike. They were seeking pay equity with federal nurses, and protesting against increased workloads and overtime. Six hours after they hit the picket lines, the provincial government pushed through legislation ordering nurses back to work. Soon after Bill 23 was passed, thousands of SUN members from around the province held a rally in Regina. Nurses regarded the legislation as a direct attack on all organized workers because it restricted the right to free collective bargaining and the right to strike. SUN members unanimously defied the legislation, calling it an unjust law. A few days later the employers applied for and received a court injunction requiring SUN leaders to order their members back to work. SUN refused to obey the injunction. On April 19, the provincial government, the employers and SUN signed a Memorandum of Understanding outlining a framework for agreement, and nurses went back to work. However, the union remained changed forever by the events of 1999.