Memberships purchased through the Roblox mobile app via iTunes, and Google Play are recurring by default and will renew at the end of their term using the original payment method. You can cancel at any time before the renewal date. If you cancel a recurring subscription, you will continue to receive membership privileges for the remainder of the already paid time. Whereas, memberships purchased through the Roblox mobile app via Windows and Amazon app stores are for a single month.
Please remember, it is better to cancel sooner rather than later to avoid being charged.
Canceling a subscription via Apple:
Follow Apple's directions to view, change, or cancel your subscription on your iPhone, iPad, or computer. Note: A Family Sharing organizer can't manage subscriptions for other family members. You will need to have the family member view, change, or cancel their subscriptions from their own devices or when they are signed in with their own Apple ID.
Canceling a subscription via Google Play:
Follow Google's directions to pause, change, or cancel a subscription on Google Play.