I wonder why "roaming"? That is normally a windoze 'hidden' folder.
Not a problem as long as you access it through krita.
However, I did have to make the patterns folder and I do not have the .kde4 in the path. This is a new krita install in a Win7 64bit VM .
2 Gimp .pat patterns dragged & dropped in, All the default krita patterns are png. (I do know that jpegs and png files also work in my more usual linux machine)
The 2 Gimp patterns show up ok in the patterns drop down.
As you indicated the krita documentation is still very sparse.