It takes some practice and I can't say I've mastered it, but I can make something that is recognizably floral, at least. (When my student, David, makes them you'd swear you can smell the rose.) I got the pastry bag, rose tip, and rose nail at Joann Crafts. Getting the slip to the right consistency took a few tries: too stiff and it won't even emerge from the bag, too thin and the flowers lose their shape. A blender worked much better for preparing the slip than hand-mixing, because mechanical blending results in fewer lumps.
Here's me, giving it a shot: