Coach - In my HOA we were given a copy of the original surveyed subdivision plat which shows each lot and the dimensions of each. This was the same thing on file at the assessor's office when I went to make sure the developers hadn't kept the mineral rights to our subdivision. Maybe you could call your HOA president or infrastructure person to save a trip downtown.
You do not own the minerals in the Right of way. You find your acreage by finding the area of your lot. The Land Caddo just leased for 30k an acre was mostly right of ways.