Can't change my country for Roblox purchases

There's no country setting on the Roblox side you can just flip. If you're buying on a phone, the price and currency come from your Apple ID or Google Play country, so that's the account you'd have to change. Apple makes you clear any store credit and subscriptions first, and Google only lets you switch once a year. On the website it goes off your payment method and where you are. A VPN mostly just gets the card declined, so I wouldn't bother.