I’m writing a poem and trying to find the right word to express a sea of white roofs – as in a city whose houses are covered in snow. I combined the nouns Dächer and See, which seemed to be the most logical choices. Does this work in a semantic sense?
Both "Dächersee" and "Dächermeer" would be comprehensible and acceptable words in the context of a poem. Outside of poetic language, a similar word, "Häusermeer", is actually even somewhat usual.
While "die weiße Dächersee" and "das weiße Dächermeer" would accurately describe the snow-covered roofs (and possibly fit with your poem), a translation that is a bit closer to the English version you provided would also work - "die See aus/von weißen Dächern" or "das Meer aus/von weißen Dächern".
would sound appropriate to me. I would translate the sea to das Meer, and not der see. See means lake when you do not us the pronoun die.