Prep: 15 minutes; Cook: 90 minutes. You can roast the beets up to 2 days before assembling salad.
Preheat oven to 350°.
Wash beets, leaving wet, and wrap individually in foil. Arrange beets in roasting pan or on baking sheet; bake 90 minutes or until tender (poke a thin-bladed knife through foil to test). Cool in foil. (To cook on stovetop, place beets in saucepan and cover with water; bring to a boil and cook over medium heat until tender. Cool. This takes less time than baking--45 minutes to an hour.) Dice beets.
Toss pears with lemon juice in a small bowl; cover, and refrigerate up to 2 hours. Place diced roasted beets and cheese in 2 separate bowls; cover, and refrigerate up to 2 hours.
Combine oil and next 5 ingredients in a bowl, stirring with whisk.
Remove pears, beets, and cheese from refrigerator 15 minutes before serving; bring to room temperature.
Place greens in a bowl; top with pears, beets, and cheese, and drizzle with vinaigrette.