This is Jess's favourite thing to do - Roll.
Whether it's rolling in worms, poop, dirt and anything else that smells... it seems the smellier the better sometimes! She's normally such a graceful and "girly" dog, I suppose this is the one rough and ready thing she really likes to do.
I never intervene when she rolls, mainly because it makes her so happy! Whether its a bit of grass or some infamous fox poo, the smell will eventually fade away with some good old bath time, so why would I ruin her happy times :)
Interestingly.. Molly has never done this. She never ever rolls, not at home, in the back garden or on our walks! Another difference in my puppies personalities.