The ornamental design for a rockdustblower, as shown and described.
FIG. 1 is a left side elevational view of a rock dust blower showing our new design, the right side being a mirror image thereof;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken lines depicting structural elements are included for the purpose of illustrating portions of the rock dust blower which form no part of the claimed design.
The broken line periphery in the FIG. 5 view defines the boundary of the claimed design.