My guess is rose slugs--teeny little green wormlike things, usually on the back side of the leaf but sometimes curving along the edge of the leaf.

In this case, the damage may already by done and the rose slug has been attacked by the good predators. But if not, the good predators will come along in a week or two after the slugs begin their chomping of the leaves. While you wait for them, you can pick the teeny green worms off and, if you have the stomach, squish them--or toss them out in the middle of the lawn. I doubt if they will find their way back.

Kate

Looks like rose slugs to me, too. Nasty little devils. Look on the underside of the leaf for them. I just squish them, myself.

Jeri

Yep looks like rose slug damage...

{{gwi:284441}}

{{gwi:284439}}

Right, thanks. I found the nasty little critters, but I barely saw them, so tiny. They are apparently all over. I don't have the time and the stomach to squish them, is there another way to get rid of them? What are the "good" predators, where are they coming from? Can I buy some? While the leaf on the attached picture is almost devoured, many new leaves are being attacked right now.

I've seen sparrows eat rose slugs here once in a great while... Wasps eat em when there very tiny. But
after they get bigger nothing eats them here that I can see..

Good predators can not keep up here...

I've used Garden Insect Spray (Spinosad) with good results..
Safer Insectide Soap has been so so this year...

Spinosad can kill bees, etc. and can burn leaves on hot days (contains oil)... Follow directions....

Here is a link that might be useful: Spinosad