The student only says that if he had one, he would present the red rose that he does not yet possess to his beloved the day of the ball so that she would dance with him. He says that she won't value him without the rose and that he will be lonely without her.
Once the student finds the beautiful red rose blooming outside his window, he brings it to her home on the day of the ball:
Then he put on his hat, and ran up to the Professor's house with the rose in his hand.
The girl, however, is scornful and rejects the red rose, saying it will not match her dress. She states, too, that she has received "real" jewels from another suitor, which are far more valuable than a mere rose.
The student is disgusted. He accuses the girl of being ungrateful and leaves her home, throwing the rose into the gutter, where it is run over by a cart's wheel.
However, the student is as ungrateful to the nightingale, who sacrificed his life to color the rose with his blood so that the student could have it, as the girl is about the rose. Neither the girl nor the student has any idea what has been sacrificed on their behalf. Both are caught in false value systems: the girl valuing items because of their monetary worth and the student rejecting love itself because the girl he has a crush on doesn't want to embrace a gift that he gave her.