Rotobrush, changing the color/fill of background AND foreground in rotobrush.

Is there any way to apply a "fill" to the inside of a rotobrush? I know I can invert foreground/background, but I want the background to be masked out to white, and the foreground rotobrush to have a solid color mask as well.

For example, the scene I am editing is a man walking down the street, I want to rotobrush the man out of this 30 second clip, make the background white. Then make the person be a solid shape/fill inside the rotobrush simutaneously.

Is there any way to achieve this effect?