I think mentioned this in another post but I will post it here as well. Make it very easy for Roscoe to get the treats out at first. Smear some peanut butter on the outside near the hole and then put some on the inside as well. Use treats that are small enough to just fall out for the first few days. Make it harder gradually. If he loves food, he will learn to love the Kong.
Good luck,
Gina