The ornamental design for a rotatablebilliardcuestand, as shown and described.
FIG. 1 is a front perspective view of the rotatable billiard cue stand of the instant invention, the cue, rack and paper roll depicted for illustration purposes only;
FIG. 2 is a front plane view;
FIG. 3 is a rear plane view thereof; and,
FIG. 4 is a top plane view thereof, the bottom is not shown having no ornamental shape.