Nedre Roasten is a lake in Femundsmarka National Park on the border of Innlandet and Trøndelag counties in Norway. The 2.29 km2 lake sits on the border of the municipalities of Engerdal in Innlandet county and Røros in Trøndelag county. Nedre Roasten is about 50 km southeast of the town of Røros and just under 9 km from the border with Sweden. The lake lies about 5 km east of the lake Femunden and about 8 km west of the lake Rogen which sits along the Swedish border.