What does the "N" in N-nitrosoamine mean/stand for?
The "N" means that the nitroso group ($\ce{-NO}$) is attached to the amine nitrogen.

So, for example, in N-nitrosomorpholine the nitroso group is attached to the nitrogen atom of the saturated, heterocyclic morpholine ring:



You could never have an "N-nitroso" group attached to a plain benzene ring, since there is no nitrogen atom in a benzene ring for the "N-" prefix to refer to.

In general, though, you would name aromatic nitroso compounds in the same way as you would those with any other substituent like 'chloro-' or 'nitro-'. For example, the following compound would is named nitrosobenzene: