Flexibly-reconfigurable roll forming (FRRF) process is recently introduced for the production of doubly-curved sheet metal surfaces with convenient change of the curvatures for each part. In FRRF, the sheet metal is deformed by a pair of small-diameter bent rollers with non-constant roll gap distribution from center to edge locations; the resulted part has two curvatures in transverse and in longitudinal directions. In this process, the sheet experiences a bending deformation before rolling, a plane strain compression during rolling, and another bending deformation after rolling. The previous finite element (FE) simulations of FRRF have been performed using 3D solid elements. In the present study, in order to increase the efficiency and accuracy of shape prediction process, the domain is decomposed into three subdomains of pre-rolling, rolling, and post-rolling deformation steps; each subdomain is solved separately by hiring an appropriate method for it. The pre-rolling and rolling deformation steps are solved only one time as the deformation is steady-state in these subdomains. For the post-rolling deformation step in which the sheet undergoes unknown curvature changes, an elastoplastic FEM with curvilinear shell elements is used with an initial stress state and accumulative plastic strain fields recorded from the other subdomains. The mathematical foundation of the method, the numerical computation procedure, and the sensitivity analysis of the method to different parameters are presented. In order to validate the numerical method with experimental data, several specimens with various dimensions are processed by FRRF and the results are compared to the numerical data.