A high-quality extra-virgin olive oil will add depth and complexity here.
Adjust oven rack to middle position and heat oven to 450 degrees. Toss potatoes with 3 tablespoons oil and salt in bowl. Transfer to rimmed baking sheet and spread into even layer. Roast until potatoes are tender and just beginning to brown, 30 to 40 minutes, stirring halfway through roasting. Let potatoes cool for 30 minutes.
Meanwhile, combine scallions, lime juice, jalapeño, cumin, paprika, pepper, garlic, allspice, and remaining ¼ cup oil in large bowl. (Cooled sweet potatoes and scallion mixture can be refrigerated, separately, for up to 24 hours; let both come to room temperature before proceeding with recipe.)
Add cilantro, almonds, and potatoes to bowl with scallion mixture and toss to combine. Serve.
