That's the question, I have a promo offer direct from Peacock, but when I log into my Roku account that manages my Peacock subscription, the offer is not available? How do I make it so I get billed directly by Peacock and get rid of the Roku management of said account?
Login to your Roku Account in the online dashboard (https://my.roku.com/account) and under Manage Account/Manage Subscriptions cancel your subscription to Peacock.
Then go to Peacock (https://www.peacocktv.com/) and sign up directly with them. If it is the 1.99/mo offer, it is on the Home page on the website.
Read the conditions on this offer from Peacock carefully. In many cases such offers are for new users only. I don't know whether Peacock would consider an account directly with them as being new when you've previously subscribed through a third party like Roku.
At any rate, canceling your existing subscription only prevents it from automatically renewing when your current prepaid subscription period expires. You will continue to be able to use it while it is in force.
As much as I would like to support Roku by subscribing through them, I prefer to make my subscriptions directly with each service. I can then view them on any platform they support (computer, mobile device, various streaming devices), not just on Roku. It also provides a clearer path to getting support if the need arises.