The Collaborative International Dictionary of English v.0.48:

Workroom \Work"room`\, n.
   Any room or apartment used especially for labor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

workroom
    n 1: room where work is done

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "workroom":
   agency, atelier, barbershop, beauty parlor, beauty shop, bench,
   butcher shop, company, concern, corporation, desk, establishment,
   facility, firm, house, installation, institution, library, loft,
   office, organization, parlor, sail loft, shop, stacks, studio,
   study, sweatshop, work site, work space, workbench, workhouse,
   working space, workplace, workshop, worktable