In 2004, Blackman-Woods was selected as the Labour candidate for the City of Durham constituency through an All-Women Shortlist. In her previous work she had been known by her maiden name, Roberta Woods, but added her husband's surname, Blackman, after selection to avoid confusion with Liberal Democrat candidate Carol Woods. Elected at the 2005 general election with a majority of 3,274, Blackman-Woods made her maiden speech to the House of Commons on 24 May 2005, making reference to the work of her predecessor Gerry Steinberg, the importance to Durham of Durham Cathedral, the University of Durham and the historic legacy of mining within the area. Blackman-Woods was a member of the Joint Committee on Statutory Instruments from 2005–2010 and has also been a member of the Education and Skills Select committee and the Business, Innovation, Science and Skills Select Committee. In 2006 she became the Parliamentary Private Secretary to the Chancellor of the Duchy of Lancaster, Hilary Armstrong. This post lasted until Armstrong returned to the backbenches when Gordon Brown became Prime Minister, but Blackman-Woods was then appointed PPS to the Secretary of State for Defence, Des Browne, in 2007. Following Des Brown's retirement to the backbenches she served as PPS to David Lammy MP as Minister of State for Higher Education. She was also Chair of the All Party Afghanistan Group from 2005 and the All Party Balanced and Sustainable Communities Group from 2007. Blackman-Woods was also a member of the Commonwealth Parliamentary Association and the Inter-Parliamentary Union throughout her Parliamentary career. In 2010, she was re-elected to Parliament with a majority of 3,067, and was appointed Shadow Minister for Business in June 2010, before being moved to shadow the Civil Society Minister by new Labour Leader Ed Miliband in October 2010. In the October 2011 shadow cabinet re-shuffle, Blackman-Woods was moved to become Shadow Minister in Communities and Local Government covering planning policy and procurement. In 2015, she was re-elected with a majority of 11,439, and was confirmed as the shadow housing minister. She resigned from the front bench in June 2016, before supporting Owen Smith in the 2016 Labour leadership election. She subsequently rejoined the front bench on Corbyn's re-election. She was re-elected in 2017 with a majority of 12,362, and in July 2017 she was appointed as a Shadow International Development Minister. On 16 July 2019 she announced that she would not be standing at the next general election for family reasons. She gave her valedictory speech in the House of Commons on 5 November 2019.