Preheat oven to 425. Place Brussels sprouts and sausage in a 15 x 10 shallow pan. Place grapes in another shallow pan. Drizzle each pan with 1 tbsp olive oil. And sprinkle with salt and pepper. Toss to coat.

Place Brussels and sausage pan on top rack and cook for 10 minutes. Carefully remove pan and stir. Return pan to top rack. Place grapes pan on bottom rack and cook both pans for 10 minutes until grapes are softened and Brussels sprouts are browned.

While the pans are in the oven, whisk together mustard and lemon juice. Transfer grapes and Brussels mixture to a large serving bowl. Add desired amount of pan drippings (I use all dripping from the sausage pan and a splash from the grapes), and the mustard mixture. Toss and serve.