I have not kept rosy barbs, but a quick Google search suggests that yes, they will eat plants so that is normal behavior. As for them eating everything, that doesn't seem like such a bad thing (better than dealing with picky eaters), unless they are out-competing other fish for food, in which case you may need to spot feed the less aggressive fish. You will also need to be careful not to overfeed!
I really like rosy barbs, and have been considering getting some, but I have too many fish already! I have gold barbs now, which I really like. I had heard they can be shy, but mine are really active and outgoing!