Hello m and Kev,
a definite "terminology" for paperweights is still missing, and for glass in general there is NEWMAN, Harold: An illustrated dictionary of Glass, Thames&Hudson 1977- a real bounty of information, but many paperweight- and millefiori- entries may be obsolete, as knowledge has broadened and deepened quite a lot since then...
For the term "rosette", the author is possibly referring to the "rosetta" bead, which is a variation of a "chevron bead", so the term has obviously intruded from bead making terminology. Beadmaking (trade beads, "slave" beads...)was very profitable for Venezia from 15th to the 18th century, with a steady decline until the beginning 19th century. "Rosetta" means "little rose" in Italian, without telling too much about what it looks like. No doubt, some of the beadmaking techniques were transferred to the millefiori production, intended for paperweights and other millefiori objects, with one main difference: the beads needed no clear glass cover or dome because of their small size, and beads needed a hole in the center, but paperweights nearly always were made with a more or less magnifying clear glass dome to enhance the inner decoration. So some of the original bead decorations may have found their way into millefiori canes, for paperweights.
Kind regards, Erhard