Elizabeth Barret Browning talks about a good many criteria for poetry. The format and objectives of eNotes precludes an in-depth discussion but we can help you get started in this large undertaking.

Among other ideas about poetry, E. B. Browning discusses these criteria in Book V:

• Humanizing requirement of poetry: it is to bring abstracts to a human level.
• Relate temporal space-time being with the spiritual being.
• Find the poetic-heroic in their own age.
• See with "double vision" so the remote is made intimate and the intimate is made understandable.
• Attend to the eternal content of poems rather to the form of poems (function over form).
• Attend to writing poetry as expression of artistic perception without an eye to critics or to favorable acceptance.
• Express in the second life of poetry the eternal truths apparent in the over-abundant suffering of the first life.

Robert Browning's poem "Childe Roland to the Dark Tower Came" demonstrates at least some of these criteria. For instance, as this poem is interpreted as a symbolic expression of how "despair" is conquered by unflinching loyalty to the "ideal," it is clear that "Childe Roland" expresses eternal concepts.

The opening stanzas illustrate the humanizing qualities poetry must posses. This quality of humanization contrasts with simple description. Poetry can render truthful descriptions of personalities or objects in nature but unless these are humanized, made vivid in terms of human emotions, joys, desires, yearnings, then the descriptions poetically fail. In other words, if we find no sympathy, no harmonic resonance within our own souls with the person or tree or child or mountain being described, poetry has failed. Browning instantly and immediately brings the villain of this poem to harmonic resonance: we sympathize on a human level though the sympathetic human impulse is repulsion.

My first thought was, he lied in every word,
           That hoary cripple, with malicious eye
           Askance to watch the working of his lie
   On mine, and mouth scarce able to afford
   Suppression of the glee, that pursed and scored
           Its edge, at one more victim gained thereby.

One further comment is that Browning also unites "Childe Roland" with the spiritual world through his description of the landscape he walks through when Nature takes on a voice through pathetic fallacy (a sub-type of personification that is applicable to personification of nature) and explains the resolution to the plight and blight he sees. Nature says that the only thing that can help the devastate condition of the landscape around the poetic persona is the "Final Judgement" and the fire of the sun that must melt (i.e., "calcine") the "clods" earth, thus setting free the prisoners of blight he beholds.

... I think I never saw
           Such starved ignoble nature; nothing throve:
           For flowers-as well expect a cedar grove!
   [...]
           You'd think; a burr had been a treasure trove.