The ornamental design for a rollablemonitorstand, as shown and described.
FIG. 1 is a front perspective view of a rollable monitor stand showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines immediately adjacent to the claim depict the bounds of the claimed design, while all other broken lines are directed to environment. The broken lines form no part of the claimed design.