If you're speaking of Roku accounts, you can link both TVs to the same Roku account, but there's no way to "merge" them. You have to factory reset one of them to link it to the other's Roku account.
How to factory reset your Roku® streaming device | Official Roku Support
If you have any subscriptions that you're paying through Roku on the one your factory reset, you should cancel them. You can see and manage any subscriptions that you have through Roku by logging into your Roku account at https://my.roku.com using the email address that's displayed on each of your Roku devices under Settings->System->About. Note that subscriptions through Roku are tied to the email address, and not your name or payment method.
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