Rolling

I took pups on the weekend to watch the training in dogs beginners class . We didn't participate just stand pups behaved very well with all the dogs around although got bored looking at them trying and wanted to show off. The only thing was she kept rolling in the grass there was nothing smelly but she did it many times in any new spot we moved to and seemed very happy with herself. She does it all the time of course but never so many times since then when I took her with the other dogs she kinda rolled on them! 
Does it mean anything except itchy back maybe?

There could be some scent there that she's rolling in but nothing visible to you.... Or she might just have an itch

Lady's been rolling quite a lot in new-cut-grass ..
1 playing field we cross takes a few minutes ..
all last week this has been much extended timewise
as madam wants to stop every few yards and spend time rolling on the grass ..

Scent from another dog but staffies get itchy in the heat the grass will keep them cool