I can't really roll my rs without making too much of an air sound... I cannot fold my tongue. I had to have my frenulum cut as I was "tongue-tied". This helped but my tongue is still fairly short.
I read this about the folding your tongue on a Wiki for rolling rs:
"Don't suffer through it if you just CAN'T. There are many studies on genetics that prove that genetics DO play a part in tongue rolling. Genetics and environment are the two factors that determine the ability to roll the tongue. The "back of the throat" rolled "r" is not that same as a rolled "r". The rule of thumb is that if you can vertically fold your tongue (or fold it), you can roll your "r"s. But if you can't fold your tongue, you will never be able to."
Most Helpful Guy
I am a native Swiss and we also roll our r's, just like in Spanish. I don't think it has anything to do with you being able to fold your tongue. The tongue should vibrate, as already described by @CountVronsky.
There are three major r's: the rolled one, the back-r (like in German or French) and the English one (which is yet very different again). In my experience, having lived in the US for some time, most Americans tend to be very bad at both the rolled and the back r. For some people genetics might play a role but I think it also has a lot to do with practice. It's like the tones in Chinese. They seem very difficult to us non-Chinese speakers but they can be learned.0