Hi,
Rotoscoping and Garbage/Matte Painting are very important features in Visual FX production.
Dedicated softwares are expensives, but Blender allows you to do it as well !
A the top of this page, you will find my last tutorial, including a ready to use setup, to do Rotoscoping and Garbage/Matte Painting in one pass in Blender.
http://3d-synthesis.com/tutorialsenglish.html
The use of a graphic tablet is recommended, but unfortunately, due to a bug in Blender, the sensitivity to pressure is lost the first time you render your mask. This said, as the provided setup includes the blur of the mask, it is usable without pressure sensitivity, even if working without this function is less comfortable.
Comments are welcome.
Philippe.