I think the scope for Rook is to provide orchestration and management for storage solutions in cloud-native environments. The way it does that is by providing a set of custom controllers and custom resources (CRDs) that you can use to deploy storage solutions that have "active reconciliation". This is also known as the "operator pattern": https://coreos.com/blog/introducing-operators.html

The ongoing management you get from the Rook operators is something you don't get from a Helm chart. The Rook operators are always running, monitoring the environment, and able to take corrective action if anything goes awry.

After you've deployed one of Rook's supported storage systems into your cluster using these operators, you can also use Rook to dynamically provision storage from these systems for your apps. For example, if you want a volume for your pod, you could declare a PersistentVolumeClaim (PVC) that will result in a Ceph RBD block device being dynamically provisioned, attached, mounted and connected to your pod by Rook.

Dynamic provisioning of other types of storage resources such as databases and buckets, similar to how it's done for volumes, is something I also think has a ton of value, as it would greatly improve the portability of all apps. I think there's great opportunity for integration between Rook and the Crossplane project (https://crossplane.io/) to enable those types of multicloud scenarios.

You may find these "Rook Intro" slides from the last Kubecon to also be informative: https://docs.google.com/presentation/d/1mXFmMZqTF3JV357ICkIG...

And here's the recording of that Kubecon talk: https://www.youtube.com/watch?v=pwVsFHy2EdE&index=2&list=PLP...

(source: i'm a maintainer on both Rook and Crossplane)