So if you train her right I think you made a very good choice because ever though she was a guard dog Cash was a sweetheart any other time and unstoppable when she was on duty .
 even to the point of chasing one or more people across the top of cars on our lot even after they cracked her skull open (no joke).

no one ever accused them of being SMART dogs
actually, I don't know much about rott's other then if you don't train them and keep them tied up in the back yard without much atttention they get very scarey to your neighbors as they lunge at the fence barking and baring their teeth with slobber flying from their jowls when you walk by.
(and of course I know that from experience, that dog is no longer around)