After reading the docs for the aws_iam_role datasource, it is my understanding that you get 1 data source back matching the name that you passed in (see: https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/iam_role)
Is there any way to get a list of IAM role ARNs that match a prefix instead? It doesn’t look like you can do it with this data source, but perhaps there is a workaround?