On a parchment-lined baking sheet, toss the pears with 1 tablespoon olive oil, salt, and pepper. Place in the oven and bake until the pear edges are golden, but the pieces are still firm, 12 to 15 minutes, turning halfway through. Tear the lettuce into bite-size pieces and place in a salad bowl.
In a small bowl, whisk together the vinegar and mustard and drizzle in the remaining 3 tablespoons olive oil to make an emulsion. Season with salt and pepper and pour over the salad. Sprinkle with the pears, almonds, green onions, and blue cheese crumbles, and serve.