Rolling Rs

Rolling Rs
 

I'm not sure if my technique is right, I roll Rs on the back of my throat, basically like the "guttural J", whilst flicking my tongue forwards (if the R is at the start of a word), seems to work fine, but I did read you had to vibrate your tongue or something, but it seems it's the back of my throat that does the most vibrating when I do it.

There are a few threads on the subject.

Here's one. Here's another.