serverless/lib/plugins/aws/deploy/compile/functions/iam-role-lambda-template.json

{
  "IamRoleLambda": {
    "Type": "AWS::IAM::Role",
    "Properties": {
      "AssumeRolePolicyDocument": {
        "Version": "2012-10-17",
        "Statement": [
          {
            "Effect": "Allow",
            "Principal": {
              "Service": [
                "lambda.amazonaws.com"
              ]
            },
            "Action": [
              "sts:AssumeRole"
            ]
          }
        ]
      },
      "Path": "/"
    }
  }
}