I used the new Pitbull, which i guess got a new LibRockConfig as well inside. But i as well updated the Config by myself as well and it did not change anything.
I had this problem as well, but solved it by updating my other Ace addons. In the end, it was Cartographer that was triggering the LibRockConfig-1.0 lua error when I tried to access the Rock menu via /pitbull. Give it a try and it should work. If not, try disabling ALL of your addons other than PitBull and start re-enabling one at a time until you find the culprit.