Preheat the oven to 425°F. Arrange the carrots on a large rimmed baking sheet and drizzle with the olive oil.
Sprinkle with the salt and cumin, shake the pan to coat the carrots, and roast them, turning once midway through, until they have softened and their edges are golden, 25 to 27 minutes.
Remove the carrots from the oven, transfer them to a serving platter, and drizzle them with the tahini glaze. Using tongs, gently toss to coat.
While the carrots are roasting, whisk the olive oil, tahini, lemon juice, silan, water, salt, and cayenne in a medium bowl until smooth and pourable, adding an additional tablespoon of water if necessary.