Droids were involved yes, but so were many slaves.
The construction of the Death Star continued for several years above Geonosis in utmost secrecy, under Admiral Wilhuff Tarkin's supervision.[9] The Empire utilized construction modules[29] operated by Wookiee slave laborers and various other species to complete the project.
http://starwars.wikia.com/wiki/Death_St ... nstruction







