The title points to William Blake's poem of the same name, and Bonta's short piece seems to answer it. Blake's rose is ruined by a hidden worm; here the rose is "in every garden," and its undoing is "private." The speaker treats this as something familiar: a loss so widespread that we all know it without discussing it.
The second stanza is more uneasy. Something about "a true but common tragedy" being placed "in a box velvet as ash" sounds like a burial, or like a keepsake handled with careful, almost decorative respect. The phrase "as if it were fit" suggests doubt. Is it right to package ordinary sorrow so neatly? The speaker seems to feel tenderness, but also a quiet discomfort with how grief gets softened and put away.
The mood is hushed and somber. The contrast of "velvet" with "ash" gives the ending a soft, chilling feel, as though comfort and decay were the same thing.