Preheat oven to 425. Place beets and carrots on a baking sheet. Drizzle with a little olive oil and sprinkle with salt and pepper. Bake for 10-15 minutes, until vegetables are tender. Remove from heat and let cool completely.
In a small bowl, whisk together ⅓ cup olive oil, balsamic vinegar, and lemon juice until vinaigrette emulsifies.
Once vegetables have cooled, toss together arugula, roasted beets and carrots, blue cheese, and vinaigrette. Serve immediately.