This recipe is adapted from Sara Foster's "Fresh Every Day" cookbook, published by Clarkson Potter, 2005.
Preheat oven to 400 degrees. Remove stem and tip end of squash; halve lengthwise. Remove seeds. Cut crosswise into 1/2-inch-thick slices; transfer to a parchment-lined baking sheet. Drizzle with olive oil, vinegar, and rosemary, tossing to coat; season with salt and pepper. Spread squash in a single layer; roast, turning once halfway, until tender and golden brown around edges, 35 to 40 minutes. Remove from oven. Reduce oven temperature to 350 degrees.
Meanwhile, combine breadcrumbs, thyme, 1/4 teaspoon salt, and 1/4 teaspoon pepper in a small bowl. Roll goat cheese rounds in breadcrumbs, pressing gently to coat well; transfer to another parchment-lined baking sheet. Cover with plastic wrap, and refrigerate until chilled.
Just before serving, transfer goat cheese rounds to oven; bake until cheese is just warm but doesn't lose its shape, 4 to 5 minutes.
In a large bowl, combine greens with 1/2 cup vinaigrette, tossing to combine. Season with salt and pepper. Mound greens on plates, and top with squash slices and goat cheese; serve immediately.