The Large Hadron Collider at CERN will start data acquisition in 2007. The ATLAS (A Toroidal LHC ApparatuS) experiment is preparing for the data handling and analysis via a series of Data Challenges and production exercises to validate its computing model and to provide useful samples of data for detector and physics studies. The last Data Challenge, begun in June 2004 and ended in early 2005, was the first performed completely in a Grid environment. Immediately afterwards, a new production activity was necessary in order to provide the event samples for the ATLAS physics workshop, taking place in June 2005 in Rome. This exercise offered a unique opportunity to estimate the reached improvements and to continue the validation of the computing model. In this paper we discuss the experience of the "Rome production" on the LHC Computing Grid infrastructure, describing the achievements, the improvements with respect to the previous Data Challenge and the problems observed, together with the lessons learned and future plans.