The ornamental design for a roomhumidifier, as shown and described.
FIG. 1 illustrates a perspective view of a room humidifier.
FIG. 2 illustrates a front view of thereof.
FIG. 3 illustrates a back view thereof.
FIG. 4 illustrates a left side view thereof.
FIG. 5 illustrates a right side view thereof.
FIG. 6 illustrates a top view thereof; and,
FIG. 7 illustrates a bottom view thereof.
In the drawings, short-medium dashed broken lines define the bounds of the claimed design and form no part of the claimed design. Short-short dashed broken lines show disclaimed features that form no part of the claimed design.