Maybe because of allergies if the dog is rolling on the grass a lot. Also, it might have got bitten.
Dogs often roll on their backs with toys as a playful or submissive behavior. This may be a way for them to engage with the toy, show their belly as a sign of trust, or simply enjoy the sensation of rolling and playing. It can be a fun and natural behavior for dogs to express their joy and playfulness.
I think, (not sure) it's because they are itching their backs
In the grass
Dogs eat grass to help digest their food.
Dogs roll in certain parts of grass to mask their scent with the smell of the grass or to mark their territory with their own scent.
Dogs perceive grass as shades of yellow and blue due to their limited color vision.
some dogs that loves to dance
Dogs aren't generally mathematicians.
dogs enjoy pooping chickens!
no
Prarie dogs eat grass and weeds.