  Recent $B$-physics results have sparkled great interest in the search for
beyond-the-Standard-Model (BSM) physics in $b\to c\ell \bar{\nu}$ transitions.
The need to analyse in a consistent manner big datasets for these searches,
using high-statistics Monte-Carlo (MC) samples, led to the development of
HAMMER, a software tool which enables to perform a fast morphing of MC-derived
templates to include BSM effects and/or alternative parameterisations of
long-distance effects, avoiding the need to re-generate simulated samples. This
paper describes the development of RooHammerModel, an interface between this
tool and the commonly-used data-fitting frameworks HistFactory and RooFit. In
this document, the structure and functionality of the user interface are
explained. Information of a public repository where it can be accessed is
provided, as well as validation and performance studies of the interface. The
methods developed in the construction of RooHammerModel can provide useful
information for alternative future attempts to interface HAMMER with other
data-fitting frameworks.
