Why are all “fossil” pokemon rock type? My friend has a theory that during their time they were not all rock types and that it is the restoration process from the fossil that gives them the type. Is there much evidence of this and what these pokemon were like in the past?

Oddly enough, I’d actually written an entry on the subject here, but suffice to say, I’d like to agree with your friend. The whole restoration process is an imprecise one at best, so errors in the rendering of pokémon—including the physiological makeup of each specimen—would hardly be surprising.