In the story The Nightingale, the red rose symbolizes love. The red rose is considered the most beautiful and the most desired flower in the world, just like love is so beautiful and so desired.
The story illustrates the Student as materialistic and selfish. The Student wants the girl in the story to love him so badly and is broken-hearted when she turns down his red rose when he finally discovers one growing in his garden. However, the Student does not realize that HE is actually selfish and ungrateful for what the Nightingale did for him. The Nightingale believed in love so deeply that she died for love by creating the red rose for the Student.
Just like a perfect red rose seems impossible for the Student to find growing in his garden, true love can also be hard to find. True love is special, unique, and not found between any two people. True love has to be cherished and nurtured.