| Name of the Candidate | Party Name | Result |
| DR. ASHOK KUMAR | Indian National Congress | 85506 |
| MANJU HAZARI | Bharatiya Janata Party | 51145 |
| INDAL PASWAN | Communist Party of India | 9543 |
| SURENDRA DAS | Rashtravadi Janata Party | 2355 |
| ARUN RAM | Independent | 2315 |
| RAM BAHADUR AZAD | Independent | 1783 |
| BALESHWAR PASWAN | Bahujan Samaj Party | 1610 |
| SHATRUDHAN KUMAR PASWAN | Samajwadi Party | 975 |
| VIJAY LAXMY DEVI | National Janta Party (Indian) | 769 |
| BAIDYANATH KUMAR | Garib Janta Dal (Secular) | 736 |
| None of the Above | None of the Above | 5841 |
| AC No | Category | Poll Phases | Last Date of Nominations | Date of Polls | Result |
| 139 | SC | Phase I | Sep 23rd 2015 | Oct 12th 2015 | Nov 8th 2015 |
Rosera legislative assembly constituency is part of Samastipur Lok Sabha constituency. It is composed of community development block; Phulhara, Lilhaul, Singhia-I, Singhia-II, Singhia-III, Mahen, Wari, Nirpur Bhaririya, Bangarahta, Hardiya, Mahra and Keothar of gram panchayats of Singhia CD Block; Shankarpur, Jakhar Dharampur, Ghiwahi, Dasaut, Rahiar North, Rahiar South, Ballipur, Bandhar, Karain, Raniparti and Rajaur Rambhadrapur gram panchayats of Shivaji Nagar CD Block.legislative assembly constituency
One of the ten assembly segments located in the Samastipur district of Bihar, Rosera, which was made reserved before for candidates belonging to the scheduled castes before the last general assembly elections to the state in 2010, is currently represented by Manju Hazari iof the BJP who emerged victorious from the seat in 2010 by defeating Pitambar of the Lalu led Rashtirya Janata Dal (RJD) by an impressive margin of 12119 votes.
Manju Hazari is the sister-in-law of Maheshwar Hazari who had won both the elections to the Warisnagar seat in 2005, then a SC reserved seat. Maheshwar Hazari’s father and veteran socialist leader Ram Sevak Hazari was elected from the seat four times. Ram Sevak Hazari who died in 2012 entered the Bihar Assembly for the first time in 1967 from Warisnagar on the ticket of Sanyukta Socialist Party (SSP). He later claimed the seat in 1969, 1985 and 2000. Ram Sevak Hazari had defeated Bishwanah Paswan in the 2010 election to Kalyanpur seat in Samastipur.
Maheshwar Hazari was relegated to the third place in the 2014 Lok Sabha elections which installed the Narendra Modi government at the centre.
Former RJD minister Pitamber Paswan had emerged winner from the Warisnagar assembly constituency in 1977, 1980, 1990 and 1995. He was elected to the Lok Sabha from the Rosera Lok Sabha constituency as an RJD candidate in 1996.Earlier Gajendra Prasad Singh of the RJD had won both the elections to the Rosera seat in 2005. On both occasions his nearest rival was Ashok Kumar of the Janata Dal (United) who had defeated the former in 2010 by an impressive margin of 19500 votes from the Warisnagar assembly seat which was derserved before 2010.
Rosera is one of the six assembly constituencies that combine to form the parliamentary constituency of Samastipur which is currently represented by Ram Chandra Paswan of the LJP who won the seat in the 2014 Lok Sabha elections by defeating his nearest Congress rival Ashok Kumar by a close margin of 6872 votes.Other five assembly constituencies that are parts of the Samastipur parliamentary seat are Hayaghat, Kusheshwar Asthan, Kalyanpur, Warisnagar and Samastipur.
CM Nitish Kumar tried to win over the youth and women, while raising the "outsider vs Bihari" (Bihari vs Bahri) issue, to seek people's support for the Grand Alliance (GA) candidates. At a well attended public meeting at Radha Krishna Mandal Govind Goswami college at Shivajinagar in Rosera for Congress candidate Ashok Kumar (Rosera seat) and JD(U)'s Ashok Kumar (Warisnagar seat), Nitish asked the youth present in the crowd to raise hands and promised a slew of youth-centric measures in his next term.Of nearly 26.17 lakh electorate in Samastipur comprising 10 assembly seats, about 35% are below the age of 30 years and may tilt the scale in favour of any candidate.