Dear Zahra,
For either collection or augmentation aggregates, catalogers may choose to provide direct access to the aggregated content through access points, or may choose to provide a formal contents note. I would lean towards viewing this publication as an augmentation aggregate rather than as a collection aggregate, as the primary content is a single poem by Frost, and the essay by Ostrowski is intended to augment and contextualize the text of the poem. In the MGD for aggregates, there is a comparable example of "An authoritative edition of the novel Persuasion by Jane Austen with associated essays."
For direct access to Frost's poem, an author access point in the 100 for Robert Frost, combined with the title in the 245, serves as the value for Manifestation: expression manifested.
100 1_ $a Frost, Robert, $d 1874-1963, $e author.
245 14 $a The road not taken [...]
If there were at least two essays in addition to the poem, I would lean towards providing a contents note for the poem and essays. However, since there is just a single essay in addition to the poem, and that essay shares a title with the poem, a formal contents note does not seem sensible here. The MGD on aggregates, in the section on augmentation aggregates (see page 8), continues by stating that "Descriptions of augmenting content are cataloger's judgment in most cases," and provides some examples that may be useful. I would thus just include a simple 500 note: 500 __ $a Essay by Susan Ostrowski, leaves 5-10. Optionally, you can add access points for Ostrowski and Dixon:
700 1_ $a Ostrowski, Susan, $e writer of supplementary textual content.
700 1_ $a Dixon, Peter S., $e editor.
Note that per the MGD Relationship Labels, the PCC will continue to use the 7 original RDA relationships such as "writer of supplementary textual content" which were subsumed in Official RDA into the relationship element "contributor person of text."
I hope that helps!
--Timothy Ryan Mendenhall