Gingered Rhubarb Crisp

Name: Gingered Rhubarb Crisp
Ingredients: 1 1/2 lb. (750 g) rhubarb stalks, cut into 1/4-inch (6-mm) slices; 3 oranges; 1 cup (8 oz./250 g) granulated sugar; 3-inch (7.5-cm) piece fresh ginger, peeled and grated; 1 1/2 cups (7 1/2 oz./235 g) all-purpose flour; 3/4 cup (6 oz./185 g) firmly packed light brown sugar; 1/2 cup (1 1/2 oz./45 g) quick-cooking rolled oats; 1/2 tsp. ground cinnamon; 1/4 tsp. salt; 6 Tbs. (3 oz./90 g) unsalted butter, melted and cooled; Vanilla ice cream for serving