Rohtas district is one of the thirty-eight districts of Bihar state, India. It came into existence when Shahabad District was bifurcated into Bhojpur & Rohtas in 1972.
The Rohtas district is a part of Patna Division, and it has an area of 3850 km² (square kilometres), a population of 2,448,762 (2001 census), and a population density of 636 persons per km². The language spoken in this area is [Bhojpuri,Hindi and English].
The administrative headquarters of the district, Sasaram is a place of historical importance. Another important symbol of national pride are the parallel bridges built over the Sone River – one for road and another for railway. The road bridge (Jawahar Setu built by Gammon India in 1963–65) over Sone was the longest (3061 m) in Asia until it was surpassed by the Mahatma Gandhi setu (5475 m) over the river Ganges at Patna. Nehru Setu, the railway bridge is the second longest railway bridge in India.
The district is also home to the Rohtasgarh fort, which was one of the strongest forts in the medieval age.
The district is currently a part of the Red Corridor.
Rohtas district occupies an area of 3,851 square kilometres (1,487 sq mi),comparatively equivalent to the Solomon Islands’ Malaita Island.
The district has a variety of landscapes within a small area, with flat plains running alongside the Kaimur Range and Rohtas Plateau. The majority of the land is a fertile floodplain of the Son River which is a tributary of the Ganges originating in Madhya Pradesh. The mountains of the Kaimur Range, which is an extension of the Vindhya Range were heavily forested in recent history, however mass deforestation has occurred due to firewood being used as fuel. The area is highly fertile and due to this is densely populated.
The climate of the region is sub-tropical and typical of the plains of Northern India, with hot dry summers and cool winters with cold nighttime temperatures. The monsoon is vital for the district as the economy is mainly based on agriculture.
Deforestation has led to climate change and has had an environmental impact, with drought becoming more frequent and temperatures becoming warmer. As recently as the early 1990s, nighttime frost used to be common in the winter, however deforestation in the Kaimur hills has had a negative impact.
Rohtas district comprises 3 Sub-divisions:
Until 1980, Dalmianagar was one of the major industrial cities in India. It had sugar, vegetable oil, cement, paper, and chemical factories (Rohtas Industries) but now they are closed. Dacoities, extortion and interference from the local mafia led to the downfall of this place. In 2008–09 budget establishment of railway factory in Dalmianagar has been passed and the campus of Dalmianagar factory has been taken by railway.
Dehri On Sone is also famous for coal depot. This market brings customers from all over of North India for coal trading. There is one hydropower generation unit which generates 6.6 megawatts of electricity.
In 2006 the Ministry of Panchayati Raj named Rohtas one of the country’s 250 most backward districts (out of a total of 640). It is one of the 36 districts in Bihar currently receiving funds from the Backward Regions Grant Fund Programme.