Sweet Potato Pecan Salad

Name: Sweet Potato Pecan Salad
Ingredients: 4 stalks celery, cut into 1-inch pieces; 2 large sweet potatoes, peeled and cut into 1-inch pieces; 1 red onion, cut into 1-inch pieces; 1/4 cup olive oil, plus more for finishing salad; 1 teaspoon ras el hanout; 1 teaspoon finely minced fresh rosemary; Kosher salt and freshly cracked black pepper; 1 cup green grapes, cut in half; 1 cup toasted pecans; 1/2 cup pomegranate seeds; 1/2 cup thinly sliced scallions; 1/4 cup golden raisins; Sherry vinegar, as needed