just to extend on this question: What's the difference between Project Browser role and Project Viewer role in Google Cloud Platform
There is already a good answer from @John Hanley. But to clarify further: what's the meaning of a "list" permission? Does "list" mean that "you can list it/view it" but "you cannot access it"? If so, the IAM role:
roles/browser
which contains the permission (https://cloud.google.com/iam/docs/understanding-roles#project-roles):
resourcemanager.projects.list
should be able to see all project's resources including Cloud Storage (as a child resource of a project)! Why then that answer states that with this role You cannot list the objects in the bucket. ? I expect you could (just) see all nested resources instead!
thanks