The ornamental design for a rollercoveradapter, as shown and described.
FIG. 1 is a perspective view of a roller cover adapter according to our design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a side view thereof;
FIG. 7 is an environmental perspective view of a roller cover adapter shown in use on a roller frame and surrounded by a roller cover; and,
FIG. 8 is an environmental side view of the roller cover adapter.
The features shown in broken lines in FIG. 3 depict optional structure and form no part of the claimed design. The roller frame and roller cover, shown in broken lines in FIG. 7 and FIG. 8 of the drawings, merely depict the environment of use of the roller cover adapter and do not form part of the claimed design.