Halo: Starside Intercept is a Homeworld 2 total conversion bringing tactical space combat to the Halo universe.
Realistically sized and detailed, you can build mines, bases and defenses on them. They'll vary in size between several meters across to several hundred meters across.
Must be a pretty large asteroid if it's become roughly spherical under it's own gravity. In fact IIRC it would then be counted as a dwarf planet.
thats...one...big...rock...