I have been saying for some time that my plants of these do not rebloom, but this year they are.
Prairie Peace is in its third summer from a small cutting. It bloomed in May. Peak bloom was early-mid May, with the last few blooms being finished by the end of May. Right now, there is one open bloom and several buds forming. The second bloom is not near as heavy as the first, but it is re-bloming. (Plus, there seems to be about 6-8 hips from the May bloom that are setting seed.)
My R. laxa plant came from OP seed I was given. It matches the description of the true species, but could still be a hybrid. This is its third or fourth year to have bloomed. (It bloomed the second year from seed.) It also bloomed in May and has lots of hips which are already coloring. It is re-blooming now and has more buds to open.
I’ll try to post later in the summer if these keep reblooming.