Roller Tinning, Rolled Solder. In printed circuit fabrication, a surface coating of tin-lead, typically 1-2 microns thick, applied to preserve solderability. Still available from some fabricators, it is a low cost surface finish, cheaper than HASL, typically used on 1-layer PCBs, sometimes 2-layer PCBs. See "Multilayer Printed Circuit Board Handbook," ed. Scarlett, JA, Electrochemical Publications, 1985, Chapter 15: Solder Finishes for more detail and history of the process.
Never used the stuff, but I can�t see 1-2 microns of anything being much of a solderability preservative. Ask who ever is that�s selling you this bridge, oooops, coating for proof that demonstrates this big improvement in wave solder defects.
Now to be fair, Sipad; maybe Optipad, Miltec, and Precision Pad Technology too; (Who can keep track??? ;-)) fabricate boards that are "in-side-out" with the pads on the inner layers showing through pockets in the laminate/mask, print and reflow paste on the pads, roll the solder to provide a flat surface, and coat that with an OSPish flux. May be that�s what you�re being sold, not "roller tinning" in the olden times sense that I�m babbling about.