Retrieve a list items from the parent site to the sub site

Question

Hello guys :D i'm trying to retrieve a list items of the parent site using rest api in sharepoint online hosted app workflow, I’ve tried to use : appURL + "_api/site/rootweb/lists/getByTitle(ListCollaborateurs)/items" but it didn’t work and I’ve got this error: result : {"error":{"code":"-2147024891,System.UnauthorizedAccessException","message":{"lang":"fr-FR","value":"Accès refusé. Vous n’êtes pas autorisé à effectuer cette action ou à accéder à cette ressource."}}}

=> French version

Any idea please, and thnx in advance :D