Rok

Roks are asteroids used by the Orks as fortress bases to launch an assault on a planet. They're full of Orks ready for the raid and their weaponry, including deadly missiles, provides a devastating cover-fire to the landing. Recently some of these flying bases have been proved to possess some kind of stealth-system which bypass the Imperial sensors, as happened on Buca III in 962.M41, which was annihilated by missiles fired from an Ork base hidden on an asteroid.

During the Third War for Armageddon, Ghazghkull mounted massive tellyportas, enabling his troops to attack using surprise and overwhelming numbers. They were also big enough to transport gargants to a planets surface.