She unionised her workplace, a Checkers branch in Vereeniging, Transvaal, and subsequently served as CCAWUSA's national treasurer from 1999 until 2009, when she was elected to hold the same office in COSATU.
[1] Her mother was a farmworker and Rantsolase's education was frequently disrupted during the political turmoil of the apartheid era; she herself became involved in anti-apartheid activism while at school.
After leaving school without matriculating,[1] she took up work at Checkers in Arcon Park in Vereeniging, part of the Vaal triangle in the former Transvaal.
[2] She was also a member of the African National Congress (ANC) and served as the chair of the disciplinary committee in the party's regional branch in Vaal.
She was one of a handful of COSATU leaders included in the ANC caucus for the explicit purpose of strengthening the union's representation in the framework of the Tripartite Alliance.
[7][8] After the election, she was appointed as the chairperson of the ANC's caucus in the National Assembly[9] and also served as the party's whip in the Portfolio Committee on Labour.