Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_20641 ( "Danish name" text, "English name" text, "Seat of administration" text, "Largest city" text, "Population (January 1, 2008)" real, "Area (km\u00b2)" real, "Pop. density (per km\u00b2)" text )

### Question ###
What is the minimum population of the region in which Roskilde is the largest city?

### Accurate SQL ###

SELECT MIN("Population (January 1, 2008)") FROM table_20641 WHERE "Largest city" = 'Roskilde'