Place the sweet potato cubes on a large oven tray and mix with the olive oil, salt and black pepper. Place in the middle of the oven and roast for 15 minutes. Take out and set aside to cool for at least 5 minutes.
While the sweet potatoes are cooling, make the tahini sauce by placing all the ingredients in a jar, screwing on a lid tightly and shaking vigorously.
Mix the arugula salad and roasted sweet potato in a bowl and mix.
Top with feta cheese.
Top with sunflower seeds and pumpkin seeds as well as tahini sauce just before serving.