Many threads on the forums say that you cannot apply a tracked point to a mask or vice versa, which is mostly true. However, last night I discovered a way you can apply position, scale, and rotation data to your mask. If you're masking an object that moves around the mask itself never changes its shape, this will work. If the mask needs to change shape, you'll need to keyframe the path property. If it only changes position, size, or rotation, this will work! (most of the time at least)
To begin, start a track of the object (one or two points, depending on what you need) you want to mask. Then, apply that tracking data to a point. Open the point, and copy ([MAC] cmd+c or [WINDOWS] ctrl+c) the position, scale, and rotation data. You have just copied all the keyframes. Now, open up the mask, open transform, and click "position" and then hit paste ([MAC] cmd+v or [WINDOWS] ctrl+v) to paste the keyframes! You will have to adjust the mask's anchor point to line it up, but it should then stay pretty much in line with the object you must mask. You can always tweak it a bit manually if needed.
Again, you'll have to manually rotoscope the path property if the object changes shape, but rotoscoping only the path is much easier than rotoscoping all four properties!
I thought this may be helpful to a number of projects as this masking technique saved me an hour of tedious work!