Preheat oven to 425 degrees. Line a roasting pan with foil, and brush with olive oil. Arrange pear slices in a single layer and brush with remaining oil. Sprinkle with salt and pepper; roast 30 minutes (turning once), or until pears are golden and edges are light brown. Cool. (This step can be done several hours ahead.)
Mix vinegar and honey in small bowl. Slowly whisk in oil until combined. Season to taste.
In large bowl, combine greens and pears. Carefully toss with dressing. Plate salad and garnish with blue cheese and pecans. 4 servings.