Using a false ID for any reason, including getting access to Roblox Voice Chat, is not only against the platform's regulations but also illegal.

How to Use Roblox Voice Chat Without ID Let’s make one thing perfectly clear: if your Roblox account isn’t 13+, you won’t be able to use this method.

Well, as you've probably surmised by this point, Roblox now has voice chat which was just released out of beta -- "Spatial voice chat," to be specific.