I work pretty much exclusively in buttercream at the moment and am shopping for some flower nails since I only have a couple. I came across one called a witch's hat that is supposedly for roses, but I can't find any information on how it works. I love making buttercream and royal icing flowers so if it's something I can learn, I want to. I've searched with google, youtube, even the forums here and nothing I come up with is relevant. Please enlighten me!

It's for making a rose. The cone is used instead of piping a frosting cone. I've never tried it, just what I've read.

I'd imagined that much. I guess I just don't understand how you'd get it off and onto anything else. If it's buttercream, it seems like it would collapse in on itself if you tried to remove it. If it's royal icing, it seems like it would be awfully fragile once removed.

This is sort of a different topic, too, but is there a REALLY GOOD, comprehensive book or website or something for how to make all kinds of buttercream flowers? I've seen the Wilton site which has a lot, but it seems like their older books have different flowers, or even different methods for making them. I was hoping there was a book or something that just had a bajillion different kinds of flowers to make.

I use the witch's hat all the time. They are no more fragile than one made with the regular nail. They seem to make it easier for some to learn how to make the rose, IMO. To get it off of there, use your flower lifter, and you spin the nail as you are lifting it off of there.

Most of the roses I make out of buttercream/royal are made with that - I personally love it.

Maybe I should get one because I can not pipe a rose on a piped cone. I pull the whole thing this way and that trying to pipe on petals and it just winds up a mess.

Here's another way of making roses that might interest you. A short clip from Cile Belleflleur Burbridge on how to make a rose using a pointed dowel. She makes hers of royal but I would think it would work quite well with a stiff buttercream.
Here's the link. Click on Cile's kitchen to see her how to's.

http://www.pem.org/sites/weddedbliss/