Roblox is built around Robux, and a large share of disputed spending is by minors. The U.S. gives these cases unusual strength. For a child under 13, the Children's Online Privacy Protection Act (COPPA) plus card-issuer unauthorized-transaction rules support reversing the charge; for teens 13–17, state contract-law (minors can often disaffirm contracts) and the unauthorized-transaction route apply. The minor-refund estimator walks the exact path by age.
Start with Roblox's own unauthorized-purchase / parental-refund process and submit proof the account holder is a minor (age, the account, the charges). Roblox does refund unauthorized minor purchases in many cases, and that is the fastest, account-safe route.
If Roblox refuses or the spend was large, open a dispute with your card issuer for the unauthorized transaction. Credit cards get the 60-day FCBA window; debit cards have shorter issuer timelines, so move quickly. The U.S. federal rights page explains both clocks.
If the issuer pushes back, escalate to the CFPB complaint portal and your state Attorney General consumer office. Keep every screenshot and receipt — minor-spend disputes win on documentation, not outrage.