I had 3 events with tree limbs where I cursed the unknown name of the dude who invented rops. Twice which raised my tractor up, and the last time a branch hooked up on one, stretched out, and then whipped forward and smacked me in the backside of the head. Oh, look at all the pretty stars!
So now, I don't keep mine just folded down...I actually flat out unbolted and removed the top of them (I got the foldable type), and just have the sides still up. So why do I still keep the sides on the tractor then, one may ask? Well that's coz I'm concerned if the tractor rolls, it's gonna roll all the way over on it's top, causing more damage to it and being harder to get it rolled back over on the wheels. If it rolls, it's gonna damage the rops because they don't have a cross member tying them at the top, but at least they'll save the tractor from further damage.
As for safety, I do NOT keep these things still on for my personal safety, instead I pretty sure I'll be able to hop off the tractor if it rolls. Whoever believes otherwise (and I heard it all already, thx) that's great. But frankly I don't care what they believe, because I trust my own judgement.