You can use your iTunes App Store Gift Card on Roblox and you will need to redeem your iTunes Gift Card into your Apple ID first.
For example, you can buy Premium 80 Robux for 99 cents. So if you want to go ahead and buy some Robox, you can choose between 10 different options. But for Roblox, this is not a problem at least at the time of this article. In Amazon if you’re purchasing something, you cannot use an iTunes Gift Card and then once you go in the app, it’s just not going to appear there. When you cannot use an iTunes Gift Card on the app, then it is not even going to have “in-app purchases” line at all and this line will not exist in that app. There are some apps that you cannot use in iTunes Gift Card.