Røldalsvatnet is a lake in Ullensvang Municipality in Vestland county, Norway. The 6.99 km2 lake is located about 35 km south of the town of Odda. The village of Røldal is located at the northern tip of the lake and the village of Botnen is located at the southern end. The European route E134 highway runs along the northern end of the lake, and the Norwegian National Road 13 runs along the western shore of the lake.