Preheat your oven to 425°F (220°C). Toss the cubed beets and sweet potatoes in olive oil, salt, and pepper. Spread them in a single layer on a baking sheet and roast for 25–30 minutes, stirring halfway through, until tender and slightly caramelized.
While the vegetables roast, combine ricotta, lemon juice, olive oil, and a pinch of salt in a blender or food processor. Blend until silky smooth. If needed, add a teaspoon of water at a time to reach a creamy, spreadable consistency.
Whisk together tahini, lemon juice, maple syrup, and enough water to get a pourable texture. Add a pinch of cumin if desired for an earthy depth. Taste and adjust for tanginess or sweetness.
Place your greens on a serving plate or large bowl. Layer roasted beets and sweet potatoes on top, then add avocado slices. Dollop or swirl the whipped ricotta over the veggies, followed by a generous drizzle of lemon-tahini sauce. Sprinkle with optional nuts, seeds, or fresh herbs for a finishing touch.