The ornamental design for roller board insert pair, as shown and described.
FIG. 1 is perspective view of a roller board insert pair shown in the non-claimed environment of a roller board assembly, each of the two roller board inserts that make up the pair being identical to one another;
FIG. 2 is an exploded view of the roller board insert pair of FIG. 1; and,
FIG. 3 is a front view of the roller board insert pair of FIG. 1, the rear view being a mirror image of the front view.
The broken lines shown in FIGS. 1-3 are for illustrative purposes only and show non-claimed portions of the roller board assembly and inserts.