Preheat the oven to 425ºF. Grease a baking sheet and set aside.
Cut the sweet potato into 1/2" rounds, then add them to a large bowl and drizzle with olive oil. Toss to coat, then season with salt and pepper. Place the rounds on the baking sheet and roast for 25 minutes, flipping halfway through.
While the sweet potatoes are roasting, add the tomatoes, hummus, lentils, 1/4 cup of water, Italian seasoning, salt and pepper into a small saucepan. Bring the mixture to a bowl and stir until everything is combined. Turn down to a simmer and let cook for 10 - 15 minutes, until the lentils are soft. Stir in additional water as needed if the sauce gets too thick.
When the sweet potatoes have softened, spoon 1 - 2 tablespoons of sauce onto each round (depending on their size) and top with shredded cheese (use vegan if needed).
Place baking sheet back in the oven and broil until cheese has melted.
Garnish with fresh herbs and pepper flakes (if desired) and serve immediately.