Consider Blake as an originator of the Romantic Movement in English Poetry.

The question you have posed is a subjective question. Therefore, the answer is subjective as well. What this means is that interpretation of anything is based solely upon a reader's or critic's interpretation of the posed question and their support of the answer.

That being said, William Blake could be considered the originator of the Romantic movement in English poetry given his artistic and imaginative works. Blake's works were, unfortunately, not recognized during his lifetime (like many authors). What one needs to understand is that periods, such as the Romantic period, were defined well after the movement began. Characteristics needed to be recognized as being followed by a greater whole so as to define a period's characteristics.

Consider the fact that many movements were created given the overall unhappiness of the previous period's work. This being said, the work of Blake did not follow the typical writing style of the period preceding the Romantic age (The Age of Reason). Blake's work was filled with complex symbols which showed his rebellion and imagination- both characteristics typical of the Romantic period. Reasoning was no longer the prominent theology of literature; instead, imagination and natural imagery were highlighted. The work of Blake epitomized both of these.

Blake depicted the Devil as the one who could fight the rules of society. This was, by far, a novel idea.