When I teach the "shake" I have them in the "sit" position, then nudge their paw up a little bit and until it is in my hand, then I reward with the treat. I am also using the clicker training method, so I actually click when the shake happens, then treat.
For the rollover, when they are in the down position, I take a treat in hand and slowly bring it close to their nose on one side of their head then kind of roll the treat over the head to the other side, they follow with their nose, then the body follows too
I also use that method for the "spin" only in a sitting or standing position, soon they do it with just the motion of the hand
Hope this helps a little
Have you tried clicker training? It's a wonderful method