Edit: Lol I say that but I see all tracks are techincally filled. I actually didn't realize that. Let me kick the people who still aren't doing anything and see whose track you can cannibalize
Yes masking is fairly basic, You have to manually cut out the character using the Pen tool frame by frame to do this though. Some people prefer working in Photoshop,AE, or Nuke when doing roto but Vegas is more then capable.