Preheat your oven to 400°F (200°C). Toss the sweet potato chunks with a drizzle of olive oil, salt, and pepper. Spread on a baking sheet and roast for 20–25 minutes or until tender and slightly caramelized. Let cool.
In a small jar, combine lime juice, olive oil, honey, Dijon mustard, salt, and pepper. Shake well.
In a large bowl, layer the mixed greens, roasted sweet potatoes, feta, and pistachios. Drizzle with the lime vinaigrette just before serving.