This is actually pretty well described in the docs.
Before you create worker nodes, you must create an IAM role with the following IAM policies:
AmazonEKSWorkerNodePolicy
AmazonEKS_CNI_Policy
AmazonEC2ContainerRegistryReadOnly
Also you need to make sure that this role could be assumed by EKS.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": "ec2.amazonaws.com"
},
"Action": "sts:AssumeRole"
}
]
}