I chose this five characteristics of romanticism:
first of all:
Imagination. To do a romantic poem you need imagination
Emotion. A romantic poem need emotion because the emotion you can express it with the words of the poem.
Nature. All romantic poems needs nature because the nature relax you of the modern world.
Symbolism. Romantic poems need symbolism to intrigue the reader.
Pastoral life. Some poems has a pastoral life that connect the reader with a simple life.