What is the MOST operationally efficient solution that meets these requirements?
Create AWS CloudFormation templates. Reuse the templates to create the necessary IAM roles in each of the AWS accounts.
Use AWS Directory Service with AWS Organizations to automatically associate the necessary IAM roles with Microsoft Active Directory users.
Use AWS Resource Access Manager with AWS Organizations to deploy and manage shared resources across the AWS accounts.
Use AWS CloudFormation StackSets with AWS Organizations to deploy and manage IAM roles for the AWS accounts.
Explanations:
While CloudFormation templates can automate the creation of IAM roles, it lacks the integration with AWS Organizations needed for efficient multi-account management.
AWS Directory Service provides user authentication but does not address the specific need to create and manage IAM roles across multiple AWS accounts.
AWS Resource Access Manager allows sharing resources but is not specifically designed for managing IAM roles across multiple AWS accounts.
AWS CloudFormation StackSets with AWS Organizations enables centralized management and automation of IAM roles across multiple AWS accounts, making it efficient.
I strategize that the answer is:
Use AWS CloudFormation StackSets with AWS Organizations to deploy and manage IAM roles for the AWS accounts.