Soak potatoes (optional): If time allows, soak the potatoes in water to cover for up to 1 hour to remove excess starch. Drain, and dry them between layers of a paper or kitchen towel.
Preheat the oven to 400ºF.
Cook the lentils according to the directions on the packet until al dente. Do not overcook them or they will be mushy. Drain, and place them on a paper towel or dish towel and gently pat dry.
Season lentils: Transfer the lentils, 1 ½ teaspoons olive oil, ½ teaspoon garlic powder, onion powder, and salt to taste to a medium bowl. Mix gently to combine. Place the lentils on a large nonstick rimmed baking sheet in an single layer. Set aside.
Season tomatoes: Transfer the tomatoes to a large bowl. Add 2 tablespoons olive oil, minced garlic, Italian seasoning, and salt and pepper to taste. Toss to coat evenly. Place the tomatoes on a large rimmed nonstick baking sheet in a single layer. Set aside.
Season potatoes: Transfer the potatoes to a medium bowl. Add 1 ½ teaspoons olive oil, ¼ teaspoon garlic powder, paprika, and salt and pepper to taste. Toss to coat evenly. Place them on a large nonstick baking sheet in a single layer.
Roast: Place the potatoes, tomatoes, and lentils in the oven and roast for about 30 minutes, or until golden brown. Toss after 15 minutes so they cook evenly. Remove the potatoes once they are fork tender and golden. Remove the lentils once crispy, and the tomatoes once they have burst and are golden brown. Set aside to cool for about 5 minutes.
Make dressing: Mix the balsamic vinegar, maple syrup, and Dijon, if using.
For serving: Serve separately as sides. Or transfer the potatoes, lentils, and tomatoes to a large bowl. Add the desired amount of the balsamic maple dressing, or your choice of dressing. Mix well to combine. Serve warm or chilled.