Only had a bit of bloat once after Ted had that GA dental, (about 24 hours after) his tummy went really bloated, but not caused by grass. I just kept rub his tummy and lots of little smelly trumps came out of him! Haha
Grass is great, that’s why I try to get them out in their run as much a possible, but you can hand pick it too for Rollie, Simon said it was the best possible thing for teeth as well as hay. Of course lack of hay eating is the first sign of things going down hill dental wise, so grass really helps. You just need to try a small bit, if ok, try a little bit more etc. Mine a totally tolerant to grass.