the blue roses are just based in a fairytale that roji adapted to her life. to explain it easier from what i understood, for roji it was like a sign that whoever gives her blue rose will be the one she marries. thats why she’s disappointed whenever her partner gives her red roses and was flabbergasted when jin gave her blue roses but then jin didn’t know what blue roses meant for roji.

Maybe I sped through it but I don't rlly understand the story? Would someone be willing to explain what the blue roses and everything mean