I set up Roku in our Airbnb using my home Roku account. I realize now that I don’t want the Airbnb Roku tied to me account. How can I change and have 2 separate accounts.
You can create a second account using a different email address. There's no cost to creating and using an account.
You could also put the BnB Roku into Guest Mode, which hides your account from the user. More info about Guest Mode here.
To switch an existing Roku setup to a different account you have to do a Factory reset to clear the existing account information from that unit.
Factory reset is accessed via Settings > System > Advanced system settings > Factory reset. This will clear out the unit's memory and you'll then have to set it up again as though it were a new unit right out of the box. During this process you can set up a new account and link to it, or you can link to an existing account you have set up ahead of time.