Heat grill; lightly oil grates. Grill bread and rosemary, turning often, until rosemary is lightly charred and bread has grill marks, about 1 minute for rosemary and 2 minutes for bread.
Strip leaves from rosemary; set aside 2 tsp. Purée garlic, remaining rosemary, vinegar and oil in a blender until smooth.
Top bread slices with ricotta and vegetables. Spoon vinaigrette over and sprinkle with reserved rosemary.