Long Haired Rottie?

Looks like it's possible but rare.  Is your friend sure he has a purebred Rottie?  Hovawarts have hair like Coke and I believe Rotts were used to re-create the breed.

 I'm not sure if he's sure...I'll have to ask.

From what I have found, its something that happens rarely, but I suppose that would make it genetic right?  He did say he knows a few people that have them, but that they are rare...

sounds to me like someone is breeding Rare Long Haired Rotties...which skeeves me out.  I had to jump off my soapbox though to make sure.  I hate to sound preechy...lol.

 I know someone who has one that does agility. It is just something that pops up in them and like long haired GSDs they can come from parents with "normal" coats. A lot of breeds have odd color/coat posibilities:

Labs: http://www.woodhavenlabs.com/mismarks.html

Dals: http://hattrick-dals.home.att.net/Colors.html

Aussies: http://www.ashgi.org/color/nonstandardcolors.htm

GSDs: http://www.4gsd.net/colours.html

 you forgot long haired english mastiffs 

http://www.youtube.com/watch?v=D8grZb5lVEM

AgileGSD

A lot of breeds have odd color/coat posibilities:

That is amazing!  I am tellin you there are a couple of those Labs that I would have sworn were a Rottie!

I fell in love with the Red aussie puppy, last one on the aussie reds, "thud"

 Yeah, they exist.  They are not a seperate breed tho.  I think it's a recessive gene, so it just gets thrown up from time to time, even from parents with normal coats.... the dog is still a pedigree, still a rottie, can even be reg'd (I think) but wouldn't make it in the show ring (long coat is a "serious fault";) and should not be bred. 

GSDs are the same at least in AKC.  They show up in normal litters if the parents have the coat factor.  Nikon has coated siblings.  They are registered just the same.  In UKC they don't care as much.  There's a coated dog around here that's been Best of Breed.