|“Why he was, in a way. He could make an entire building disappear in just a matter of seconds! He was the kingdom's greatest demolitions expert. And then one day, he just quit. No one knows why! He might be just the man to help us out!”|
|— Merlok 2.0 in "The Stranger in the Halps"|
Prior to the series
Slab was once a great demolitions expert known as the Great Rockowski. Merlok was one of his close allies and they fought together on many occasions. At some point, he stopped destroying, got a house in the Halps, a rabbit, a rock named Donny that he chose to "befriend," and became sort of a "hippie" type. He also began to make "tree art."
While trapped in the Halps, the Nexo Knights did not know what to do, but Merlok 2.0 told them to keep driving in order to find a house belonging to Slab Rockowski. However, they were surprised to find that he had become lazy. Merlok tried to convince him to destroy the Stone Monsters, but Slab refused, stating that he stopped destroying many years ago.
When Jestro, Monstrox and the Stone Monsters (as well as the new Rubblers) attacked the house, they began to destroy the tree art, making Slab angry. Slab surprisingly grabbed two rocks and began to destroy all of the Stone Monsters quickly. When they couldn't be destroyed fast enough, he rolled Donny across the mountain, destroying more Rubblers.
After Monstrox's defeat, Slab stayed at his house with Bunny.
- His name is a play on the words "slab" (a type of stone) and "rock," as he uses rocks to demolish opponents.
- He is portrayed by the late Kirby Morrow, who portrayed a character associated with rocks, Cole, in another LEGO theme, Ninjago.