I would like to create a billing policy in the Power Platform admin center, but there is no New billing policy button.
I think I need to set up security roles, can you tell me how to set up predefined security roles for users?

I would like to create a billing policy in the Power Platform admin center, but there is no New billing policy button.
I think I need to set up security roles, can you tell me how to set up predefined security roles for users?
Here is the list of security roles that can set up a billing policy in the admin center.
Set up a pay-as-you-go plan - Power Platform | Microsoft Learn
And this article walks you through how to assign Security roles in the Power Platform admin center.