Remove about half the grapes from their stems, leaving the remainder in several small clusters. This gives you beautiful presentation grapes along with individual grapes that collapse and become almost jammy.
Whisk together the Balsamic Jam, olive oil, orange juice, black pepper and kosher salt. Toss with the grapes and rosemary and spread them in a shallow roasting pan.
Roast for 18–22 minutes, stirring the loose grapes once, until some have burst and their juices have mingled with the Balsamic Jam to form a glossy sauce. Remove the rosemary sprigs and toss the warm grapes with 1 teaspoon orange zest.
For the ricotta, combine the milk, cream and salt in a heavy saucepan. Heat gently until steaming with small bubbles around the edge, but do not boil. Remove from the heat, stir in the lemon juice and leave undisturbed for 10 minutes.
Drain through cheesecloth until creamy but still soft. While slightly warm, gently fold in the orange zest, honey and several turns of black pepper. Don't whip it completely smooth—I would keep those beautiful soft homemade curds.
For the crostini, melt the butter over medium heat and continue cooking until the milk solids become golden and the butter smells nutty. Add the olive oil. Toast the baguette slices in batches until deeply golden on both sides. Immediately rub one side lightly with the cut garlic.