For the Romantics, nature and imagination are the most important elements.Discuss this with references to the poems "Rime of the Ancient Mariner,"...

I guess I have to diverge a bit from the phrasing of the
question.  I think that Romantics were not able to separate the embrace of
individuality, the love of nature, moral structure, exploration of the imaginative
powers of the self, establishment of artistic autonomy, and the exploration of the
subjective in the world into a hierarchical fashion.  They all seemed to converge into
forming the Romantic creed of beliefs and values.  Even in the poems featured, I find it
difficult to establish one idea as more dominant than other elements.  Certainly,
Coleridge's poem features nature and a sense of moral imagination being expanded, but
there is an equal emphasis on being able to identify a structure that governs human
behavior in the killing of animals.  This is as prevalent as nature and imagination. 
Wordsworth's ode to maturation is just as dependent on nature and imagination as it is
on the lauding of the personal with "the child as the father of the man."  The works
from Keats and Shelley are just as concerned with the role of the artist and how the
artist conceives the universe and his/ her individual setting just as powerfully as
imagination and nature galvanizes them.