Answer :
You would need to include the center of rotation. For many problems, the center is usually the origin (0,0). This is a default assumed center. Though the center could easily be any other point.
In addition, you also need the amount of rotation that is being applied (eg: 90 degrees).
The last bit of info you need is whether you're going clockwise or counterclockwise. For 180 degree rotations, it doesn't matter, but for everything else it does matter.