az role assignment create fails for custom role

[kbroughton]

Version:
I'm unable to discover the version, but it was downloaded within the last 2 months.

Description:

I was able to create a custom role according to https://docs.microsoft.com/en-us/azure/role-based-access-control/custom-roles

however,

az role show -n "my role name"

as shown in the docs, does not work
https://github.com/Azure/azure-cli-samples/blob/master/identity/rbac.md

Listing as follows works

az role definition list --custom-role-only true

I attempted to associate according to the docs

az role assignment create --role <my role> --assignee friend@example.com --resource-group <my group>

Fails with Role 'my role' doesn't exist.

I was able to make the role association via the azure portal
Home > Resource groups > "Select the Resource group" > Access Control (IAM) | "Click + Add" | "Select the user or group and role"

Expected results:
I would expect that az role show -n would work and associating would also work according to the docs.