If that happened here in our garden I would suspect White Fly-but they leave the roses pretty much alone for now.

They really sound like whitefly. Aphids don't do that.

If that's what they are, they aren't colonizing roses, but you will find thier nest clusters and the webbing under the leaves of other sorts of plants. (See photo, below)

Look for plants like fibrous begonias. We see them on begonias, plumerias and brugmansias, but I'm sure they do other sorts of things.

If that's what they are, DO NOT use insecticides. That will only kill beneficials, and make things far worse. When we sprayed, we had a lot of trouble with them.

The infestation shown below was very bad, but localized. I removed the worst-affected leaves, and rubbed some of it off with my fingers, and blasted the whole thing with high-pressure water.

Jeri

White flies have been extremely bad in the Santa Clarita Valley this year, even with the intense heat. Hollyhocks and most of the annuals have been infested. The roses have remained unaffected. None of the plants here in my more arid garden in Encino, not even the hibiscus, have experienced any white fly. Ironic, but true. Kim

In Tennessee, the insects that are out now are wooly hackberry aphids. They are out by the trillions.

You won't see the aphid for the mass of not-cotton on their backs and the not-cotton lets them float around.

Their preferred habitat is (duh) hackberry trees of which Tennessee has billions.

The worst part is that they poop and anything under them gets the poop and the poop grows black (and it takes hard scrubbing to get it off of trucks (ask my husband about his old blue pick up) and even stop signs that you won't see the stop part of the sign.

The only positive is that the fall lady beetles that are such pests coming into homes in fall will eat some of the wooly hackberry aphids. Not enough, though.

Ok. Great info! Just so ya know I would never spray insecticide. I don't kill bugs unless I can smush em. Seen lots of wooly caterpillars this year...do they make butterflies?
Jeri, I haven't noticed any evidence of webbing or "habitat making"--it's just clouds of white critters rise up when I disturb canes.
Ann, Wooly Hackberry aphids sound like just what these critters might be and yes, I have seen black droppings on rose petals.There is a (nasty) hackberry tree two yards over.
I have those lady beetles who get into my house so YAY maybe they will pig out before crashing the house party!
Thanks everybody!
Susan

Would blasting them with a high-pressure water hose help?

Jeri

Worth a shot. I love blasting insects from my roses. I've noticed some white critters on my buds too...
I've taken to firing a BB gun in the vicinity of the squirrel marauders who eat ALL my seed.
I'm feeling like Annie Oakley!
Susan

Annie Oakley! LOL

We drove into town this morning, and it was overcast, with no sun peaking through.

It was a really interesting look at the trees that have grown over our roads. Many many of them are hackberry trees. It's an easy ID, because of the "shadows" under the trees on days with shade.

Look at your roads that are asphalt that is now a light gray. You'll see black on them as if it were shade, but it's not.