Hey @straight-sunset-92336,
Hmm. Import creates code & state to manage the resource, but I believe the built-in roles are immutable & can't be modified by Pulumi.
I don't see that role definition when I run the Azure CLI, either, so I wonder if this might be behind a feature flag. Is this a recently added role definition to Azure?
I found some code we use to manage Azure IAM here at Pulumi, and it looks like this is how we create role assignments. I modified it a bit and pasted it in as a snippet above.