We do need a report like the default "aggregated folder" report but excluding the sub-folders. This means the root folders should be added to the parameters and the export should include the aggregated folder size (in MB) for each root folder only. The sub-folders should not be displayed or part of the report, but for sure the size need to be calculated.
Folder structure on file server;
ROOT-folder: 0 MB
Sub-folder 1: 10 MB
Sub-folder 2: 10 MB
ROOT-folder: 20 MB