Before you can set up 2-Step Verification for your Roblox account you'll need to download Roblox Authenticator App on your device by searching for it in your Apple device's App Store or click on the button below Download on the App Store.

Sign in to your Roblox account, click on the gear symbol at the top right corner, and select Settings.

Under the Security section click the toggle switch to turn on Authenticator App (Very Secure)

In this step is shown the QR Code that contains the secret key which you need to scan with Authenticator App. Keep the page open as you reach for your device.
Note: Do not scan the DEMO QR Code shown below.

Open Authenticator App, tap the plus button, and hold your device up to the computer screen to scan the QR Code from Roblox web page.

After successfully scanning the QR Code given by Roblox, Authenticator App will automatically choose the Roblox logo and autofill the account name and secret key. Click on Save when ready.
Tip: You can choose the account icon by pressing on icon

Returning to the Roblox web page, type in the six digit code from Authenticator App in the appropriate field. When done click Verify.

You have successfully enabled two-factor authentication (2FA) to protect your Roblox account, from now on, you will need to use the Authenticator App when you would like to log in to your Roblox account.