Does my entire organization need to use fluxroll?

No. Teams within a larger organization can still derive all the benefits of fluxroll by on-boarding just their artifacts and instrumenting their deployments.

What is an artifact

An artifact is an application or service that your team builds and deploys. Example: Rails/Django application, microservices.

It could also include external services (ex. Managed Databases/Redis) that you don't build but still depend on. Tag such artifacts as resources so it is easy to identify them.

Do I need to identify dependencies between artifacts to use fluxroll?

You can start using fluxroll without identifying dependencies. This still allows you to see the timeline of changes within your organization. You can add dependencies as you identify them.