Peel and halve pears; core, if desired. Place, cut side up, in 13- x 9-inch (3 L) glass baking dish.
In a small bowl, whisk together oil, sugar, and lemon juice; brush all over pears.
Roast in 425°F (220°C) oven, basting once, until caramelized and tender, about 40 minutes. Let cool in pan.
Transfer 1 tsp (5 mL) of the pan juices to a small glass measure for vinaigrette.
For the Pear Vinaigrette: Add vinegar, oil, shallots, salt, and pepper to the reserved pan juices in the glass measure.
In a large bowl, toss together salad greens, radicchio, and vinaigrette; divide among plates.
Slice pear halves into quarters if desired, arrange on salads, and sprinkle with almonds.
