Preheat oven to 375°F and line a baking sheet with aluminum foil. Cut the butternut squash in half, scoop out the seeds, and place on the baking sheet, covering with aluminum foil. Place in the oven, and roast for 45 minutes to an hour, until the squash can be just pierced with a fork. Let cool. While the squash is cooling, chop and wash the lettuce, and divide among four bowls. When the squash is cooled, place the cut side down, and remove the skin with a sharp knife. Cut it into ¼ inch thick slices, then cut crosswise, making butternut squash cubes. Measure two cups of the cooked, cubed squash, and divide evenly among the salads. Cut the pear into quarters, thinly slice each quarter, and top each salad. Do the same with the blue cheese and walnuts.