Change username on ROBLOX

You have to go to account settings, which is the cog on the top bar menu, then go to "Account Info" and find your username. Once you see your username, click the pencil to the right of your name and choose a name.

This process costs 1000 Robux though. Ensure you have the required funds for this.

Go to your profile and click settings next to username and there should be a pencil and paper click that then enter your new username you want

Go to your settings at https://web.roblox.com/my/account#!/info , then under Account Info, click the pencil icon near the username field. Change the username to whatever you want, then confirm your transaction with a R$1000 fee.