In "Open House," Theodore Roethke likens the poetic process to making himself a metaphorical open house of sorts. He explains that he lays his very sense of self onto the page and hides nothing in the process.
In the first stanza, the speaker—presumably Roethke speaking as himself—says that his "secrets cry aloud." In this juxtaposition of "secrets" and "cry," the reader is brought to understand one of the contrasts of poetry: taking that which is deeply personal and explicating it for a wide audience.
Therefore, nothing is personal because everything is shared. His heart itself, then, becomes an "open house" as he invites readers in to examine the emotions he feels passionately. The poetry he creates on the page is an "epic of the eyes," and he makes no effort to diminish the emotions he experiences, because writing poetry is his great passion.
It has been said that authors sometimes feel that they metaphorically bleed onto each page in order to share themselves and their experiences with readers and that it is such a deeply personal process that it is sometimes painful. This sentiment is felt in the second stanza as the speaker describes being "naked to the bone" as all of his truths are poured out onto the page. He hides behind nothing; he wears only his own truth and his own experience as he shares both his life's anguish and its truths.
The last stanza has a dark undercurrent of his poetic experience. It is not love that will endure through his poetry but anger. Through his poetry, he is able to "speak the truth" by keeping his language honest and "strict," meaning that he doesn't dance around with ornate modifiers and language. To borrow from the previous stanza, he keeps the "spirit spare," focusing on the raw emotions of experience instead. His poetry propels him forward, and rage itself shapes the course of his writing as he faces it in "agony" and cries out to the world through the truth of poetry.