EKS Pod Identity Webhook, which is described more in depth here, allows you to provide the role name using an annotation on a service account associated with your pod.

⚠️ WARNING: aws-eks auth has been deprecated and support for it will be removed from KEDA on v3. We strongly encourage the migration to aws auth.

You can tell KEDA to use EKS Pod Identity Webhook via podIdentity.provider.

podIdentity:
  provider: aws-eks # Optional. Default: none