Changing your Username in Roblox will cost you 1,000 Robux, equivalent to $14.98. Whereas, the display name feature debuted in 2021 which is different than changing your username.

A Display Name is how other players will see you in-game. This feature appeared in 2021 and is available to all players free of charge. While Usernames are unique, two or more players can have the ...

ROBLOX allows you to change this username, as well as your Display Name. It’s important to note that there are different rules and applications of both Usernames and Display Names.