Poetic devices are used by poets to create the images and sounds they want in a poem.
The most prevalent device found in the poem is personification and extended metaphor.
A metaphor is a comparison between two unlike things. An extended metaphor is a metaphor that continues for several lines or, as in this case, an entire poem. In this case, the rose is compared to a person who is exploring faith.
Personification is describing something nonhuman with human characteristics.
A Rose, in tatters on the garden path,
Cried out to God and murmured 'gainst His Wrath (lines 1-2)
“Ere yet the stars saw one another plain” (line 16)
A rose cannot cry, or talk. Throughout the poem, the rose thinks and has a conversation with God. Stars do not have eyes to see each other.
Those lines are also an example of rhyme, “path” and “wrath” rhyme, and the poem is written in couplets, or pairs of rhyming lines.
Simile is a comparison of two unlike things using like or as.
“softly as a rain-mist on the sward” (line 13)
Alliteration is the repetition of initial consonant sounds.
“Whereat the withered flower” (line 19)
Imagery is descriptive language that appeals to the five senses and creates an image for the reader. There is plenty of imagery in the poem. Here are some phrases that evoke the senses.
Sight: “A Rose, in tatters on the garden path” (line 1)
Sound: “a sudden wind at twilight's hush” (line 3)
Touch: “Then softly as a rain-mist on the sward” (line 13)