Filter Reports based on Company Region

I am working on an application for a mortgage lending company. This company will have regions servicing homes in different areas in the United States. Borrowers will be the ones creating records in the user portal, and those records will be assigned to an account manager in a region assigned to the state the property is located in.

The trouble comes with regional managers that need read and write access to only the deals assigned to their account managers. From how I understand role hierarchies, higher levels can view records created by lower levels, but I don't think this wouldn't work in my situation where external users are creating the records and the records are then assigned to account managers. Is there a way I can create filtered reports for these regional managers?