Give a brief prose paraphrase of "The Snow Man" by Wallace Stevens and "Desert Places" by Robert Frost remarking general similarities or differences in subject matter, speaker and point of view. Also, concentrate on descriptive details, noting any significant parallels or divergences in wording or meaning.
I think you mean "give a brief prose paraphrase" AND "remark on general similarities," etc. A paraphrase, in itself, would be a rewording of the poem into prose. This rewording would contain no commentary, comparisons, contrasts, or parallels; however, I will be happy to look at the list of other things you mention as separate from the paraphrases. Let's begin with the paraphrases you request.
Paraphrase of "The Snow Man"
One would have to think as winter thinks in order not to see misery in the landscape: the frost, the snow, the cold, the ice, etc. There is even sadness in the sounds: the wind, the leaves, the land, etc. The listener will understand the word "nothing" both in the landscape and in himself.
Paraphrase of "Desert Places"
Snow is falling and it is quickly getting dark. I looked at a field as I went past it and saw it covered with snow except for a few bits of weeds and grass. There is a forest surrounding it. I am not even aware enough to see that I am lonely as well. Further, it will get more lonely before it gets less lonely. More and more whiteness will cover the ground and hide everything. There is no need to be afraid of space that doesn't contain human life. I have enough to fear within myself.
Now to attempt a bit of commentary on these two poems. Both do have similar subject matter: the desolation of winter that leads to introspection. In both cases, the poet waits until the end of the poem to use the words to compare them to both the speaker (as in "Desert Places") and to the speaker and the reader (as in "The Snow Man"). How do we know this? Because in "Desert Places" Robert Frost specifically uses the word "I."
I have it in me so much nearer home
To scare myself with my own desert places.
In "The Snow Man," Stevens specifically uses the words "the listener" which could be ANYONE, including the reader.
For the listener, who listens in the snow,
And, nothing himself, beholds
Nothing that is not there and the nothing that is.
Focusing on descriptive details, there are quite a few similarities in regard to winter. For example, "junipers shagged with ice" by Stevens could rightly be compared to "the ground almost smooth covered in snow." Stevens, of course, gives a lot more detail, even in speaking of the kinds of trees. Frost speaks generally of "the woods" and the effect of the snow on them. The result, however, is similar: pessimism. Stevens concentrates on nothingness and Frost concentrates on loneliness. In this case, it is Frost that is more specific about the emotion while Stevens' "nothingness" could be most any bereft emotion.
Thus, the subject matter, culmination in emotion, difference in detail, and difference in speaker make these two poems perfect for a compare and contrast essay.