ROSILLOS MOUNTAINS. The Rosillos Mountains (centered at 29°32' N, 103°15' W) are nine miles north of Panther Junction and just north of Big Bend National Park in south central Brewster County. The highest point in the mountains is Rosillos Peak, which rises 5,445 feet above sea level, some 2,165 feet above the Rosillos Mountain Ranch, just to the east. The Rosillos Mountains are a roughly circular range seven miles across. They are massive and rounded but have an internally structureless appearance, indicating that they are part of a large intrusive igneous mass. The local shallow stony soils support scrub brush and grasses.