All I know is that Necromancy was banned from the Mages Guild because it is considered a dark magic. And all the necromancers I can find are evil and just send ghosts and zombies after me.
Jauffre wouldn't be able to die if you still needed him for the main quest so I wouldn't worry toooo much.
I heard that once you get to the highest rank in the Mages Guild you get some kickass necromancy spells. Any truth to this? I just became Arch-Mage and I don't seem to have any or see a NPC around that sells them. I wanted a skeleton army...
I think all you get in the line of necromancy is skeleton/zombie summons
If you REALLY want to ressurect someone, hit the console button (` just like HL2) click on their body, and type out "ressurect" and hit enter, it should bring them back to life