OK, for the less incurious, I found this in Larousse Gastronomique:
"Professional pastrycooks use various specialized rolling pins; fluted metal pins to pattern the surface of caramel or almond paste; fluted wooden pins to roll out puff pastry (this keeps the pieces of butter separate and ensures uniform distribution)...'
From The Cooks' Catalogue (1st ed., Beard, Glaser, Wolf, Kafka, Witty, eds):
"In the loose amalgam which is pastry dough, the fat must always, by one means or another, retain its separate identity--it must not, in other words, soak into the flour. When a flour-and-water dough is stacked in hundreds of layers separated by layers of butter--that is, when it is being transformed into puff pastry--the segregation is even more essential. And although any good-quality plain rolling pin can be used to make puff pastry, the ultimate instrument for this purpose is the French grooved rolling pin with the trade name Tutove: the manufacturer proudly calls it a "magic rolling pin" The magic lies in the 1/8" grooves which run lengthwise on the wooden roller; the rounded ribs separating the grooves distribute the butter evenly between the layers as the dough is rolled and as the layers become thinner and thinner and multiply in number with subsequent folding and rollings. The bite of the grooved pin is also effective in softening the dough when the pin is used to beat it after it has been chilled between workings. Made of hardwood, with black plastic handles, this is an expensive piece of equipment, but worth the price if you intend to make puff pastry: bouchees, puff-paste croissants, vol-au-vents, napoleons, crust for beef Wellington, or any number of delights."
From Child & Beck:
"The French Tutove pin is sometimes available in import stores; its cannellated surface is designed especially for distributing butter evenly throughout the dough when you roll puff pastry or croissants."