If you want to add new Roles and Features to a Nano Server then you have to do it when you create the image file with the New-NanoServerImage using the optional package parameter. For more details on how to create a new image check this. You can also add new roles and features with the edit-nanoserverimage . fs
The available packages for a nano image can be found on the installation iso/DVD in nanoserver\packages subdirectory.
edit-nanoserverimage -basepath d:\nanoserver -targetpath c:\nanoservers\nano1.vhdx -packages microsoft-nanoserver-dns-package