Coat a baking sheet with no-stick spray.
Spread the potatoes and tomatoes over the prepared baking sheet and coat lightly with no-stick spray.
Sprinkle with the rosemary and coarse salt.
Bake at 400° for 40 to 50 minutes, shaking the baking sheet once or twice to keep the vegetables from sticking, until the potatoes are browned and the tomatoes are very tender and have a dark sweet crust.
Arrange the lettuce leaves on a serving platter or on 4 individual salad plates.
Sprinkle the roasted vegetables with the vinegar and serve on top of the lettuce leaves.