Roasted sweet potato already has plenty of sweetness. It rarely needs a sweet dressing as well. Lemon, salt, and tahini offer a more interesting contrast, with crisp vegetables alongside if you have them.
Halve two medium sweet potatoes lengthwise. Rub the cut sides lightly with oil and roast cut-side down at 200°C / 390°F until tender, roughly 35–50 minutes depending on thickness. Turn one carefully to check the surface and pierce the middle to judge doneness.
Stir two tablespoons tahini with a tablespoon lemon juice. It may thicken at first. Add water gradually until it becomes a pouring sauce, then season to taste.
Serve the potatoes with warmed chickpeas and the dressing. Chopped cucumber or cabbage gives the soft flesh something crisp to sit against. Tahini contains sesame; if that is unsuitable, choose a dressing that fits the eater's needs instead of presenting a seed paste as automatically allergy-friendly.