Preheat oven to 425 F. Toss grapes together with balsamic vinegar and olive oil. Place on a roasting pan or lipped backing sheet and roast for 10 minutes.
While they are roasting mix together walnuts, lemon juice, salt, and pepper.
When grapes are finished, add them to walnut mixture and include all the juices too.
Mix it all together.
Place arugula in a large bowl and add the roasted grape/walnut mixture.
Toss together and then sprinkle with goat cheese.