Back in the day, I only read Flash sporadically, except during the first two or three years of the Post-Crisis run. I remember Flash's lineup of baddies being collectively called his "Rouges Gallery" in the Silver-Bronze Age and it seemed like several of them would periodically associate, but no more so than Batman's or Superman's steady dance partners of the same era. There was certainly no sense that they were particularly closely affiliated.

So, when did this whole thing of The Rogues being some sort of organization become a thing?