Get good food like hot dogs or lunch meat something real tasty. Then lure the dog into a down hod the food in your hand on the dogs nose so they can lick at it but cannot get to food. If the dog is rolled on a hip that is great if not that is ok. Take the food and have the dog licking at it, take the food th make the dog look hard to the right or left what ever way will be easiest. When the dogs neck is craned over the shoulder keep going and it forces the dog the roll over and release the treat so he can eat it. Try both ways and you will find your dog can roll over better to one side. It is a little hard to explain and you might have to help them flip a few times till they understand. You keep practicing every day a few times day and they will learn it quick.
haha that was a hard one, but I ended up teaching Mel dead dog instead, I find it adorable when I introduce him to people. I ask their names and if its Sally (or whatever the name I insert) I tell him "hey Mel would you rather be a dead dog or Sally?" and he slowly becomes a dead dog, lol. sometimes he would accidentally roll over. Now he has them down pat and can do them both. Just keep trying, it will click one day!