The ornamental design for a multi-rotor rotorcraft, as shown and described.
FIG. 1 is a perspective view of a multi-rotor rotorcraft showing the new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines shown in the drawings represent portions of the multi-rotor rotorcraft that form no part of the claimed design. The shading lines shown in the drawings represent the three-dimensional contour of the claimed design and are not intended to indicate surface decoration.