There is a newly added functionality in ACM that validates whether the ARN roles are correctly configured when the user clicks on the “Save” button. If the ARN is not configured correctly, the user will see an error message "This AWS Role ARN has no read rights". If the ARN is configured correctly, the user will see a “Verified” notification next to the ARN role.
A similar functionality also works for validating S3 buckets in Accounts > Options > AWS Detailed Bill section. Once the user enters an S3 bucket name, the user will see a “Check Now” button that appears in the S3 bucket field that confirms whether the S3 bucket is verified or not.