Prerequisite: My account must have right to access to all projects
1 - Go to project A admin
1 - Create snapshot of Rolling in Compute Engine / Snapshots
2 - Create new Compute Engine instance from Rolling's snapshot
3 - Uncheck "delete boot disk when deleting instance" and delete the new instance
4 - Go to in Compute Engine / Images then create an image from this disk.
5 - Go to project B admin then create new Compute Engine instance with boot disk is image from project A