They are almost certainly Robins Pincushion Galls also known as the Bedegaur gall.
I have just copied this from this website
http://www.bugsandweeds.co.uk/
The 'causer' in this case is a gall wasp (Diplolepis rosae) which lays its eggs in either the leaves or stem of the dog rose. One gall may contain several grubs, each in an individual chamber. Subsequently, other insects may invade the gall in order to parasitise the gall wasp grubs. The gall grubs will overwinter inside the 'apparently' dead gall, to emerge next Spring.
If you google it you'll get loads of info