Format error while using join function in Terraform

Question

I would need to have joined values from schemasREAD.usage_roles together with string suffix "_R" ultimately creating a role in resource "warehouse_grant_usageREAD_R" called "PROD_FINANCE_DELIVERY_COMMONDATA_READER_R" however getting following error when using "join" function:

│   on schemas.tf line 62, in resource "snowflake_warehouse_grant" "warehouse_grant_usageREAD_R":
│   62:   roles         =  "${join("", [ "${each.value.usage_roles}" , "_R"])}" 
│     ├────────────────
│     │ each.value.usage_roles will be known only after apply
│ 
│ Inappropriate value for attribute "roles": set of string required.

Structure looks as following:

locals {
  schemasREAD = {
    "COMMONDATA" = {
      database    = "PROD_FINANCE_DELIVERY"
      usage_roles = ["PROD_FINANCE_DELIVERY_COMMONDATA_READER"]
    }
  }
}

resource "snowflake_warehouse_grant" "warehouse_grant_usageREAD_R" {
  depends_on    = [snowflake_role.role]
  for_each      = local.schemasREAD
  warehouse_name = "PROD_FINANCE_DELIVERY_LOAD_WH"
  privilege     = "USAGE"
  roles         =  "${join("", [ "${each.value.usage_roles}" , "_R"])}" 
  with_grant_option = false
}