The rose shouldnt have even been there if you are on Iorveths path because Philippa destroyed it to cure Saskia. I hope this will be fixed with the Triss tweaks.
I do not think it will be fixed, as the game does not really care much about the choices imported from TW2 in general, and the developers would probably not see it as a significant enough issue. There could at least be different dialogue about the rose and the earrings in response to the romance choice, it would only be a couple of lines for each, but it was not seen in the leaked subtitles.
Another interesting thing to note is that Phillipa says the rose is dying in Vergen (Iorveth's path). We can conclude that Geralt's love for Triss was fading as he regained his memories, or that the elven legend was false.
Is it shown that he regains any memories between the Rose of Remembrance quest and talking to Philippa that would explain the change ? I do not remember exactly (although I am currently replaying the game, and will soon begin chapter 2 on Iorveth's path), but I think he regained the most important memories later, in chapter 3.
Rose is dying cos it's not with Triss anymore in TW2. It's in Phill's hand remember?
Could the compression possibly matter as well ? I mean, maybe the rose also dies if the person it belongs to is dead (or turned into an inanimate object).
But the easiest explanation is that it is indeed just an elven legend. Even if it has some magical properties, the rose is still only a plant, and dies after a while once picked.