Prepare the Yams: Preheat your oven to 425°F (220°C). Line a large baking sheet with parchment paper. Thoroughly scrub and dry the yams, then slice them in half lengthwise. Rub 1 tablespoon of extra virgin olive oil over the cut surfaces and place them cut-side down on the prepared sheet. Roast for 20 minutes.
Spice the Chickpeas: While the yams have their initial roast, gently warm the remaining 2 tablespoons of olive oil in a small skillet over low heat. Add the smoked paprika, cumin, coriander, and sumac. Stir constantly for 30-45 seconds until fragrant, being careful not to scorch the spices. In a medium bowl, pour the fragrant oil over the rinsed and dried chickpeas and toss until evenly coated.
Roast Everything Together: After 20 minutes, remove the yams from the oven and carefully flip them cut-side up. Spread the coated chickpeas in a single layer on a second parchment-lined baking sheet. Place both baking sheets back into the oven and roast for an additional 15-20 minutes, until the yams are fork-tender and the chickpeas are golden and slightly crisped.
Make the Tahini Drizzle: While everything roasts, whisk together the tahini, cold water, lemon juice, grated garlic, maple syrup, and sea salt in a small bowl. The mixture may seize up at first; continue whisking vigorously for about a minute until it becomes smooth and creamy. If it's too thick, add more cold water, one tablespoon at a time, until it reaches a pourable consistency.
Toss the Herb Salad: In a separate bowl, combine the diced cherry tomatoes, Persian cucumber, chopped parsley, and minced red onion. Drizzle with 2 tablespoons of lemon juice and 1 tablespoon of olive oil. Gently toss to combine.
Assemble and Serve: Place one roasted yam half on each plate. Gently fluff the flesh with a fork. Top generously with the crispy spiced chickpeas, a spoonful of the fresh herb salad, and a liberal drizzle of the lemon-tahini sauce. Serve immediately.