Roskilde , located west of Copenhagen on the Danish island of Zealand, is the main city in Roskilde Municipality. With a population of 49,297 (as of 1 January 2015), the city is a business and educational centre for the region and the 10th largest city in Denmark. Roskilde is governed by the administrative council of Roskilde Municipality. Joy Mogensen, a Social Democrat, has been mayor since 2011.