Heat oven to 400°F (205°C). Combine olive oil, grapes, olives, 1 teaspoon rosemary, a couple pinches of sea salt and pepper flakes in a baking dish or roasting pan. Roast until grapes are wilted and leaking juices, about 35 to 55 minutes, rolling ingredients around in pan a few times throughout roasting time to encourage even cooking.

Slather each toast with ricotta, then heap each with grapes, olives and their pan juices. Finish with remaining rosemary and eat immediately.