While the dough is thawing, make the oven roasted tomatoes.
Preheat oven to 325°. Slice the Roma tomatoes into ¼” thick slices and toss them gently with a little bit of olive oil. Arrange on a parchment lined baking sheet, that has been sprayed with non-stick spray, and sprinkle lightly with garlic salt. Roast for about 30 minutes. When the tomatoes are done, but still hot, use a spatula to gently loosen them from the parchment (so they don’t stick.) Allow to cool to room temperature.
When the dough has thawed completely, divide it into 4 equal pieces and place on a floured board or countertop. Roll out each piece into a rectangle, about 1/4” thick. Brush the top side with olive oil, if desired, and sprinkle with a little bit of sea salt.
Place the rolled out dough, oiled side down, onto a preheated grill pan or non-stick skillet (medium-high heat.) While it starts to grill, brush the top side with olive oil. Grill about 2 minutes per side or until golden.
Remove from the grill pan and spread each Flatbread with a layer of Pesto sauce. Arrange slices of fresh Mozzarella cheese on top of each and place them in a 325° oven just until the cheese starts to melt (about 4-5 minutes.) Add a slice of oven roasted tomato on top of the melty cheese slices. (If desired, you could add slices of grilled chicken.)
Serve warm. This recipe makes 4 large flatbreads. If you are using these as an appetizer, slice them crosswise into 2” strips.