Rosera

The geographic coordinates of Rosera Assembly constituency are: 25°49'07.7"N 86°04'26.0"E. This constituency falls in Samastipur district of Bihar and in the Mithila region. Rosera shares its borders with seven other Assembly constituencies. Other Bihar Assembly constituencies adjacent to Rosera are: Warisnagar, Bibhutipur, Cheria Bariarpur, Hasanpur, Kushehswar Asthan, Gaura Bauram, Benipur. This constituency shares an inter-state border with .

There were a total of 329872 registered voters on the electoral rolls for the 2025 Assembly election in Rosera Assembly constituency, of which 175993 were male, 153876 female and 3 of the third gender. In the 2020 Assembly elections, there were a total of 330203 registered voters, of which 175406 were male, 154790 female and 7 from the third gender. In the 2015 Assembly elections, there were a total of 295959 registered voters, of which 157640 were male, 138314 female and 140 from the third gender. In 2010 elections, there were a total of 248885 registered voters in this constituency, of which 131504 were male and 117381 female and 135 from the third gender.

The number of service voters in this Assembly constituency was 224 in 2020, 5 in 2015, and 0 in 2010.

The electorate gender ratio (number of female voters per 1000 male voters) in this constituency in 2025 was 874, in 2020 it was 882, 877 in 2015, and 893 in 2010.

Rosera Assembly constituency will go to the polls in Phase 1 of the 2025 Bihar Assembly elections on Thursday, November 6, 2025. The counting of votes is on Friday, November 14, 2025.

In the 2020 state Assembly elections, this seat voted in Phase 2 on Tuesday, November 3, 2020 and the results were declared on Tuesday, November 10, 2020.

In the 2015 state Assembly elections, this seat voted in Phase 1 on Monday, October 12, 2015 and the results were declared on Sunday, November 8, 2015.

In the 2010 polls, this constituency voted in Phase 2 on Sunday, October 24, 2010 and the results were declared on Wednesday, November 24, 2010.

Assembly constituency no.139. Rosera comprises of the following areas of Samastipur district in the Mithila region of Bihar: CD Block Rosera; Gram Panchayats Phulhara, Lilhaul, Singhia-I, Singhia-II, Singhia-III, Mahen, Wari, Nirpur Bhaririya, Bangarahta, Hardiya, Mahra, Keothar of Singhia CD Block; Gram Panchayats Shankarpur, Jakhar Dharampur, Ghiwahi, Dasaut, Rahiar North, Rahiar South, Ballipur, Bandhar, Karian South, Raniparti & Rajaur Rambhadrapur of Shivaji Nagar CD Block

This constituency covers an approximate area of 264.4 square kilometers and the geographic coordinates of Rosera is: 25°49'07.7"N 86°04'26.0"E.

A total of seven Assembly constituencies in the state of Bihar share borders with Rosera constituency, which are: Warisnagar, Bibhutipur, Cheria Bariarpur, Hasanpur, Kushehswar Asthan, Gaura Bauram, Benipur. This constituency shares an inter-state border with .

According to data released by the Election Commission of India, in the 2025 Bihar Assembly elections, the estimated voter turnout in this Rosera constituency was 67.17%. In 2020, this seat registered a turnout of 55.1%, while it was 54.95% in 2015, and 51.39% in 2010.

In the 2020 Bihar Assembly elections, Birendra Kumar of BJP won in this constituency beating Nagendra Kumar Vikal of INC by a margin of 35744 votes which was 19.65% of the total votes cast. In 2015, Dr Ashok Kumar of INC was the winner in this seat beating Manju Hazari of BJP by a margin of 34361 votes which was 21.14% of the total votes polled in the constituency. In the 2010 Assembly elections, Manju Hajari of BJP won this seat defeating Pitamber Paswan of RJD by a margin of 12119 votes which was 9.47% of the total votes polled for the seat.

In the 2020 Bihar Assembly elections, Birendra Kumar of BJP had a vote share of 47.93% in this seat. In the 2015 Assembly elections, Dr Ashok Kumar of INC got a vote share of 52.59% , In the 2010 Assembly elections, Manju Hajari of BJP got a vote share of 45.29% in Rosera.