The position of Rollmaster is one of the oldest House positions in the Dark Brotherhood along with Quaestor and Aedile. The Rollmaster, before the concept of the database, was charged with keeping an accurate roll of the House's membership.
The position became unnecessary upon the creation of the database system by the then-serving Master At Arms, Thedek. The position was kept by all Clans and nearly all Houses as an auxiliary command position but for the most part it was no longer required.
Then, in 28 ABY, the Society of Envoys was closed due to its steady stagnation. Rollmasters became important once more, taking on many of the envoy duties, including the upkeep and welcoming of new members.
The Rollmaster's job is to manage the roll, as the name suggests, although in the end, it is up to the Clan Leaders what they actually do. In some cases, Rollmasters may be the ones to welcome new members to the clan or the managers of the Master-Student Program. If a Rollmaster is not appointed, the position’s responsibilities pass up to the Aedile, and then on to the Quaestor.