1-1/2 cups pitted, firm black and or green olives that have not been marinated or oil-cured, drained and patted dry. Make sure these are just plain, unsalted olives. It is easier to find black ones, so it is safer to go with those.
What to do:
Preheat oven to 350'. Grease 2 shallow baking dishes with olive oil.
Warm 2-1/2 tsp. oil with 1 tsp rosemary in skillet over medium-low heat 2 to 3 minutes, stirring occasionally. Remove from heat; stir in walnuts and salt.
Whisk together vinegar and agave nectar in bowl. Stir in grapes, olives, and remaining 1-1/2 tsp. rosemary. Spread mixture in remaining baking dish.
Roast walnuts 9 to 12 minutes in oven, or until golden-brown. Remove, and cool. Increase oven heat to 400'. Roast olives and grapes 20 to 25 minutes in oven, or until sauce is syrupy, stirring occasionally. Cool 10 minutes, stirring occasionally. Cool 10 minutes, stirring occasionally. Sprinkle walnut pieces over grapes and olives, and serve warm.