Keats famously wrote that a poet was a kind of 'physician' to humanity whose job was to 'pour out a balm onto the world.' Of course, this 'balm' was created partly by a focus on nature as a source of solace to the sufferings and trials of life. This is an aspect of Romanticism that can most clearly be seen in 'Ode to a Nightingale' when the speaker achieves a transcended state and is able to fly with the nightingale metaphorically through his poetry:
Away! away! for I will fly to thee,
Not charioted by Bacchus and his pards,
But on the viewless wings of Poesy,
Though the dull brain perplexeds and retards...
Thus poetry and its influence is able to help the speaker leave the earth, which is characterised as a place of 'no light' and of suffering in which man is forced to joylessly live until his death.
Another aspect of Romanticism which we can see in the poetry of Keats is the way that meditation on beauty can give us a real appreciation of life and the beauty within life. This can be seen in the focus on the eternal beauty in 'Ode to a Grecian Urn':
When old age shall this generation waste,
Thou shalt remain, in midst of other woe
Than ours, a friend to man, to whom thou say'st
'Beauty is truth, truth beauty,'--that is all
Ye know on earth, and all ye need to know.
Note how beauty is shown to be able to instruct humanity on some important truths that are necessary for our survivial. The urn is therefore called 'a friend to man.'
Thus by its focus on the beauty of nature and its healing influence and the meditations on beauty, Keats establishes himself as a truly Romantic poet.