1. Preheat oven to 425°.
2. In a medium saucepan over medium heat, combine rice, 1/4 teaspoon salt, 2 cups broth, and 1 cup water; cover and bring to a boil. Reduce to a simmer and cook, covered, until rice is tender (about 45 minutes).
3. Meanwhile, line a baking sheet with foil. Place turkey on sheet and coat with oil. Season with remaining 1/4 teaspoon salt and 1/2 teaspoon pepper and brush with 1 1/2 teaspoons soy sauce. Roast, turning halfway through, until turkey is cooked and a meat thermometer inserted in the center reads 165° (50-55 minutes). Remove from oven and transfer turkey to a cutting board. Tent with foil and let rest (about 5 minutes).
4. Stir spinach, scallions, and remaining 1 1/2 teaspoons soy sauce into rice with remaining 1 cup warmed broth. Thinly slice turkey. Divide rice and sliced turkey among 4 bowls; drizzle each with sesame oil and sprinkle with sesame seeds, if desired.