A google search on the matter took me to an explanation of the genetics that provided a wonderful surprise:
In humans, the ability to flute (roll) one's tongue is a dominant allele F to the inability to flute the tongue, f. A student who cannot flute his tongue has a nephew who cannot flute his tongue; however, the nephew's mother(the student's sister) can flute her tongue. etc. . .How odd that the ability to control the folding of the tongue, which I believe is necessary for making a good sound on the flute, is called fluting!
My experience with fluting the tongue is highly personal and certainly not scientific. I have never had a flute student who couldn't flute his or her tougue, and I haven't found any studies that address the matter, but would love to know if anyone reading this who cannot flute his or her tongue has had trouble trying to make a good sound on the flute.