Preheat oven to 350 degrees F. Spread the sweet potatoes in a single layer on a rimmed baking sheet (use two if needed) and drizzle with 2 teaspoons vegetable oil and the sesame oil. Mix the potatoes so they are evenly coated and season with ¼ teaspoon salt. Place the sheet on the middle rack of the oven and roast for 30 to 40 minutes, or until the edges of the potatoes turn crisp.
Then, heat the broiler to high. In a small bowl, mix the agave, soy sauce, and ginger. Drizzle mixture over the potatoes, then broil for five to seven minutes, shaking the baking sheet(s) occasionally, until nicely browned on the outside and tender inside, about five minutes. Remove from the oven and set aside to cool.
To serve, divide arugula between plates and top with sweet potatoes and chicken. Garnish with chopped scallions and sesame seeds.