Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper or foil.
In a large bowl, combine the broccoli, oil, salt, and pepper. Arrange the broccoli and lemon slices in a single layer on a baking sheet. Roast 15 minutes, stir, and roast another 15 minutes until golden brown.
In a medium bowl, combine the yogurt, tahini, lemon juice, and salt; mix well.
Spread the tahini sauce on a platter or large plate and top with broccoli and lemon slices. Garnish with sesame seeds.