Roth became a Member of the German Bundestag for the first time in 1998, entering as the directly elected representative of the Hersfeld constituency with 51.7 percent of the first vote. In 2002 he was re-elected to the Bundestag with 54.9 percent of the first vote of the newly merged constituency of Werra-Meißner – Hersfeld-Rotenburg. In subsequent elections he received 51.7 percent (2005), 40.4 percent (2009), 43.1 (2013) and 41.2 (2017) of the first vote.