Official Reveals

Gigalith was first seen on June 27, 2010, in an Oha Suta (Japanese TV program) episode, which revealed 3vs3 battles.

It was officially revealed in a Pokemon Sunday (another Japanese TV program) on August 7, 2010. 

A CoroCoro scan showing Gigalith (August 10, 2010)

Another scan from the same period, showing Gigalith's characteristics 

For Roggenrola, here is a CoroCoro Scan from September 2010 (around the 10th) revealing it.

For Boldore, there were rumors about it, among other rumors, around the same time as the Roggenrola scan.