Verden and Rottenberg were in the Kindom of Hannover (Saxony). It seems very clear that those would be the present day towns for you to search in.

I have a Michelin Regional Map #541 of the Niedersachsen area which shows Rottenberg and Verden all the other little towns. You can buy those maps online. I have a researcher who is checking on my ancestors in Visselhoevede and Verden next month. I can give you his name if you need help there.