There are Roblox gift cards that you can purchase at other retailers, which can be redeemed through a browser to credit the same account that you log into from the mobile app: https://en.help.roblox.com/hc/en-us/articles/203312720-Where...

So it's not really entering a credit card number per se; it's more like giving someone else your credit card number so they can give you another number that you type into a different portal to make the digital goods "appear" on the iOS app.

Why are they making children jump through all these hoops just to enjoy an online video game https://en.help.roblox.com/hc/en-us/articles/115005566223