Quite in remote of Samastipur district lies Rosera which has been elevated to sub-division status in recent years. Administratively it was only a block earlier. Because of being a rail-head, and an important commercial centre in the days of river trade that a small township existed here since the early decades of 19th century.

Historically, once the rail and road communication developed, the volume of trade substantially dwindled pushing the township to a stage of decline though it is one of the oldest municipal towns in Bihar. The total urban area is only 2.03 sq. kms as recorded in 1991-census. Ravages of floods as well as innumerable ditches, nullahs rivulets, chaurs etc. have also made it somewhat inaccessible. Battered roads, and near-collapsing bridges also prevent any faster road-communication. There is also no impetus in the economy of the region that could impel faster communication. Even the rail-bead is on a meter guage loop-line on which plying of trains may not be more than a few pairs.

Rosera sub-division is part of Samastipur district which was itself a sub-division of old Darbhanga district. In Rosera sub-division besides Rosera block, Singhia, Hansapur and Bibhutipur are the other three blocks. Waris-Nagar block is also adjacent to Rosera and for much of its population Rosera is in closer proximity. Khodabandpur a remote block of Begusarai district is also in close touch.