Roto Brush - It is not working at all

I'm not sure why Rotobrush is not working. Create a comp from the footage, drag Rotobrush over the part you want to keep, propagate, fix the edges if you need to, then Freeze.

If that doesn't work and you want to keep the white wall, and there is camera movement, duplicate the layer, use Mocha AE to motion track the left edge of the white wall, apply that motion to a solid, and create a simple mask. Set the layer as a matte source for the original footage. The wall is now isolated. Using the Paint workspace makes this easier.

Do the same thing for the Sofa. Just motion-track the shot, apply the transformation tracking data to a solid layer and add a mask. Combine the two mattes, and you can preserve everything except the back wall. 

Unless there is something that I'm missing, I probably would not use Rotobrush on the shot. A little motion tracking, a couple of simple masks on two different layers, a pre-comp and a track matte is all that would be required to poke a hole in the shot.