Yorkies are very smart dogs and they get their bad rep as being hard to train by people who are lazy to train them. If they aren't stimulated they will act out.
The easiest way to train them is to remember to lead their nose with a treat. Where their head moves the body will follow. This is the easy way to teach roll over. After they get "lay down" put the treat over their shoulder and have their head slowly follow until they have to roll over to get it.
And since Duchess knows how to play football, how about basketball? You can get a little hoop in the Nerf section of the toy store. Uni loves basketball.