Add 1 cup black lentils and 1/2 teaspoon salt to a small saucepan. Add just enough water to cover. Bring to a boil, then reduce heat to medium low, cover and simmer until tender (about 20 minutes). (Make sure to watch the water level of the lentils while they cook - continue to add small amounts to ensure that the lentils remain covered, but you want to avoid adding too much as it will cause them to lose their color).
Move oven rack to lower middle position and heat to 425°F. Toss together the cauliflower, carrots, brussels sprouts, asparagus, garlic, olive oil, cumin, smoked paprika, 1/2 teaspoon salt, cinnamon, coriander, and cayenne in a large bowl. Spread the vegetable mixture on a large baking sheet and cook until softened and golden brown, about 25-30 minutes, stirring every 10 minutes.
Transfer the roasted vegetables to a large serving bowl. Top with the cooked lentils.
Tahini Dressing
Whisk together the tahini, olive oil, lemon juice, salt, and cayenne. If the dressing is too thick for your taste, add water in very small amounts until you get the consistency you like.
Pour the dressing over the lentils and vegetables. Toss, if desired. Serve warm, room temperature, or cold.
Notes
Instead of using both brussels sprouts and asparagus, you can use 8 ounces of either one of them. Or you could substitute with an equal amount of broccoli.