You won't find any automated way to delete a Roblox account on its website. Use one of the 3 methods listed in the post to delete Roblox.

Display names play a vital role in online games, and Roblox is no exception. While creating a new Roblox account, choosing a fancy name may not seem important to you. However, players regret it later ...

To get or change a Roblox Display Name, you should first log in to your Account Info page under Settings, then select the edit button next to the Display Name entry above your Username.