Hallo Scott
I now spend a couple of hours about your question, because I was absolutely sure that this signature is not Rosenthal. This signature is absolutely un common for Rosenthal, but in the end I ended like you at Rosenthal.
It seems that Rosenthal gave a couple of productions to Riedel, a good glass company, themself are more experts to porcelain. These productions I have the feeling are marked with the crown over the R. Rosenthal since ages is marking with Rosenthal and the crown in the middle over the word.
I found a couple of vases in this green and light pink, all marked with this single R and the crown. Some of them mention that Phillip Rosenthal himself made the design.
In the end this is all nothing new, but you had a question which might be never answered properly. I don‘ :Dt n know if Rosenthal will answer if you ask them directly. A lot of designers worked for Rosenthal, why not Wagenfeld, but the design I know of Wagenfeld is normally a lot thinner. This could be even an Scandinavian designer, Per Lütgen of Holmegaard made a lot of quite as looking designs, but so far I know, he did not work for Rosenthal.
Maybe you are just satisfied with designed by Phillip Rosenthal
https://www.rubylane.com/item/1195515-PICT7197/Glass-Vase-Philipp-Rosenthal-Green-clubhttps://picclick.de/Well-shaped-formschöne-50´s-design-Philip-Rosenthal-323789506726.html
Monika