Preheat the oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, whisk together the maple syrup, oil, lemon juice, and salt. Add the sweet potatoes and toss to coat with the maple syrup mixture. Spread the potatoes on the baking sheet and roast, stirring occasionally, for 30 minutes, or until tender. Remove from the oven and set aside to cool slightly.
In a skillet over medium heat, toast the pumpkin seeds for 2 minutes, or until they turn golden and begin to pop. Shake the pan often during toasting to make sure they don't burn. Transfer to a plate and set aside.
In a large bowl, toss the kale with the vinaigrette. With clean hands, massage the dressing into the kale for 1 minute.
Divide the kale among 4 serving plates and top with the reserved sweet potatoes, reserved pumpkin seeds, and dates.