As early as 1070, Adam von Bremen referred to Roskilde as "Zealand's largest town". At the time of the Reformation in 1536, it had some 6,000 inhabitants but as a result of war, fire and disease, by 1753 its population had dropped to only 1,550. By the 1860s, it had grown to around 5,000 and by the 1900s to some 9,000. Thereafter it increased appreciably until 1970 when there were almost 45,000 inhabitants. The population dipped slightly to 40,000 in the 1980s, but thanks to improved connections with Copenhagen and the establishment of the university, it grew steadily to reach 47,117 by 2014 making Roskilde Denmark's tenth largest city.
In Roskilde Municipality as of 1 October 2014, 76,545 residents had Danish background, 6,287 were immigrants and 2,006 were second or third generation descendants of immigrants. The most common countries of birth of foreign-born residents of Roskilde Municipality are Turkey, Iraq, Poland and Afghanistan.
Roskilde is governed by the administrative council of Roskilde Municipality. Following the local elections of November 2013, Joy Mogensen (born 1980), a Social Democrat, was reappointed mayor (first elected mayor in 2011), gaining three additional seats on the council. The council now consists of 13 seats for the Social Democrats, one for the Social Liberal Party, one for the Conservative People's Party, one for the Socialist People's Party, three for the People's Party, nine for the Left Liberal Party and three for the RedGreen Alliance.
In the 1890s, 37% of Roskilde's economy was in crafts and manufacturing industry with only 15% in administration and services. By 1984, industry had dropped to 16% while services had risen to 57%. In 2002, services had reached 62%, leaving industry at 15% and trade and transport at 22%.
Located on the site of a 10th-century wooden church, the cathedral was built in the 12th and 13th centuries when the Romanesque style was influenced by Gothic trends from northern France. It was the first Gothic cathedral in Scandinavia to be built of brick, resulting in the spread of this style throughout northern Europe. With its 39 royal tombs, the cathedral is to this day the burial site for Danish monarchs. Since 1995, it has been listed as a UNESCO World Heritage Site, encouraging some 100,000 tourists to visit it each year. The cathedral houses a museum on its upper floor, tracing the building's history. A working church, it also hosts concerts throughout the year.