Roberts was first elected to Wrexham County Borough Council in 1991 for the Rhos and Ponciau ward. In 2003–2004 he served as Mayor of Wrexham. The council was under no overall control at the time, and in March 2005 he took over as leader of the council following the resignation of the Labour leader of the council.[10] In the 2011 National Assembly for Wales election, Roberts was elected as an Assembly Member for North Wales. Upon his election to the Welsh Assembly, he resigned as leader of Wrexham Borough Council as he felt he could not devote time to both bodies, and he did not contest the council election for his former seat in 2012.[11]
Shortly after Roberts' election as an AM, it was discovered that he was a member of the Valuation Tribunal for Wales, which was a proscribed body of which AMs were not allowed to be a member, because of a perceived conflict of interest. As a result, Roberts was disqualified from the Welsh Assembly.[12] Roberts stated that he was following a Welsh language guidance document from the Electoral Commission. This document later emerged to have been incorrect, as while the English regulations had been updated in 2010, the Welsh document still gave information based on 2006 regulations.[12] In July 2011, Roberts' disqualification was overturned by the Assembly on a 30–20 vote.[13]