Yuck! My dog Luke loves to roll in many things.
I have incorporated the word "leave it" so if he is sniffing around and I see him go in for the roll I can usually stop him (not always). I have also convinced him it is a great idea to bring the dead things to me when he finds them when we're out.
Though, One time he did roll in horse poo where I couldn't see him with my friends English Pointer. Needless to say the pointer went from white to brown and I had to take them home in the car to bath them. Unfortunately, No black hole with shampoo for me :P