Board Thread:ROBLOX help and discussion/@comment-33116234-20171125170220/@comment-4196050-20171125170939

The minifigures themselves might be copyrighted, or if you used anything related to the Ninjago line. ROBLOX is a competitor of Lego (and ROBLOX has a history of copyright issues with Lego), so it makes sense that ROBLOX would not want to deal with anything that might remotely be a copyright issue with Lego.

If I'm remembering correctly, ROBLOX's ToS prevents you from uploading anything that is copyrighted. It's a legal issue (ROBLOX was sued a few years ago by Cinemark because of players creating Cinemark theatre games).