The ornamental design for the roof box for automobile, as shown and described.
FIG. 1 is a perspective view of front, top and right side of the roof box for automobile showing my new design;
FIG. 2 is a perspective view of rear, top and right side thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof, and a right side view being a mirror image thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown are included for the purpose of illustrating the unclaimed portions of the roof box for automobile and form no part of the claimed design.