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.

Roblox system will constantly monitor the activity of an account and if you haven’t signed in to it in one year or 365 days, Roblox will automatically delete it.

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