Arugula-Stuffed Leg of Lamb with Roasted Spring Vegetables

In a 12-inch heavy skillet over medium-high heat, cook garlic in olive oil, stirring, until it begins to turn pale golden, then add arugula in batches, stirring and turning over with tongs until slightly wilted before adding each new batch, and continue sautéing until completely wilted, about 1 minute more. Season with salt, and transfer arugula filling to a large sieve set over a bowl to drain. Let cool.