Preheat oven to 400°F (200°C).
Toss sweet potato cubes with 1 tablespoon olive oil, salt, and pepper on a rimmed baking sheet.
Roast sweet potatoes for 25-30 minutes until tender and slightly browned, flipping halfway through.
Rinse quinoa in a fine-mesh strainer; combine with vegetable broth in a medium saucepan and bring to a boil.
Reduce heat to low, cover, and simmer quinoa for 15 minutes until liquid is absorbed.
Remove quinoa from heat and let sit covered for 5 minutes, then fluff with a fork.
In a large bowl, whisk together remaining 2 tablespoons olive oil, lemon juice, maple syrup, mustard, and garlic.
Add kale to the dressing and massage with hands for 2 minutes until leaves are softened and reduced in volume.
Add the cooked quinoa and roasted sweet potatoes to the bowl with kale and toss thoroughly.
Garnish with toasted pumpkin seeds and serve warm or at room temperature.