Preheat oven to 425°F (220°C). Drizzle olive oil over a large baking sheet and season with salt.
Place sweet potatoes cut-side down. Drizzle the tops with olive oil and season with salt and pepper.
Roast for about 25 minutes, then flip the sweet potatoes. Add the pecans to the baking sheet and roast for another 5 minutes. Remove the pecans and continue roasting the sweet potatoes until tender, about 35 minutes total.
For the crumble, roughly chop the toasted pecans, then add the dates, feta, and arugula, chopping everything together until you have a chunky crumble. Mix in salt, pepper, and lemon zest.
Place the roasted sweet potatoes on a serving plate and gently press the centers with a fork.
Top generously with the pecan-feta-date crumble and drizzle with the tahini-balsamic sauce.
