The international gaming giant has more than 80 million daily users, and is hugely popular with children.
It was started by Dave Baszucki and Erik Cassel, and Dave Baszucki is now CEO.
In his first ever BBC interview, he tells us about developing the game, the struggle to monetize it, and concerns over child safety - Mr Baszucki insists Roblox is vigilant in protecting its users.
Presenter: Zoe Kleinman
Producers: Georgina Hayes and Imran Rahman-Jones