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.

How to delete a Roblox account permanently? There is no option for a player to simply deactivate or delete his or her Roblox account under game settings, just like other social media accounts or ...

It’s worth noting that you can access extra Admin commands, as opposed to the original ROBLOX Admin commands, by adding an admin command Pack to your game (such as HD Admin).

You can delete a Roblox account by simply emailing the company, but there are a few other ways to do it.