Had the same issue. It did not work until I set up "Trust relationships" for the role I created.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": [
          "lambda.amazonaws.com",
          "textract.amazonaws.com"
        ]
      },
      "Action": "sts:AssumeRole"
    }
  ]
}