The round, spiky objects you see in the photos above and below are galls. But unlike the previously mentioned goldenrod gall (see here) there’s a cinipid wasp behind the gall. The goldenrod gall is caused by a fly not a wasp.
The small, spiny rose gall wasp (Diplolepis bicolor) laid eggs on the plant, in this case swamp rose (Rosa palustris), and the resultant larvae that hatched from the eggs began eating the plant. This stimulates the plant into growing a gall around the larvae.
I removed one of the galls from the rose bush and dissected it. There were eight chambers where larvae had been feeding.
The larvae remain in the gall over winter, pupate, and emerge as adult spiny rose gall wasps the following spring. The adult is a tiny wasp with blackish head and thorax, and reddish abdomen.
Below are two of swamp rose hips, or fruit.