Step 1

Preheat oven to 450 degrees. Line a rimmed baking sheet with parchment paper. Place potatoes on sheet. Drizzle with oil, season with salt and pepper, and toss to coat. Roast for 15 minutes. Add tomatoes to potatoes on baking sheet; toss. Cook until potatoes are tender and tomatoes are lightly browned and soft, about 10 minutes.

Step 2

In a medium bowl, toss arugula with 2 tablespoons vinaigrette. Arrange roasted vegetables, arugula, tuna, and olives on platter; drizzle with remaining vinaigrette. Serve.