I just followed creating Azure ScaleSet tutorial,and selected Windows scale set. As Parameters, I provided admin username as "admin" for testing. When I start the deployment it started creating storage accounts, public IP etc. and suddenly it failed complaining that the username is not strong enough.
But when I check my Azure resources, I found those storage accounts and other resources being created. Isn't there a roll back process to rollback these resources?
The concept behind ARM is that everything is managed at the Resource Group level. That doesn't matter whether you're talking about a single storage account or a thousand VMs. If a deployment doesn't work the way to rollback is to simply delete the resource group and everything contained in it will be deleted as well.
from the Azure Resource Manager overview
All of the resources in your group should share the same lifecycle. You will deploy, update and delete them together. If one resource, such as a database server, needs to exist on a different deployment cycle it should be in another resource group.
Like most other things in IT the important part is deciding where the lines of division should go. Personally I try to keep a resource group as a discreet service, so a DB, a scale set, front end web servers. That way each individual unit can be swapped out without affecting the other parts.