Why does my dog roll on his back outside?

Why does my dog roll on his back outside?

Dogs roll on their backs to show submissiveness or trust, and as an act of defense when fighting. They might also roll around on a toy, food or something they find during play or while exploring outside.

Should I let my dog roll in the grass?

Rolling in grass is not dangerous in itself. Just be sure your dog has flea and tick protection, and be mindful of potential hazards like pesticides and herbicides that might be on the grass. Even absent any foul-smelling residue on his coat, your dog may need a good rinse post-roll.