Italian architect, active mainly in Rome. Some of his works might be described as transitional between the High and Late Baroque. This is less obvious in his ecclesiastical than his secular buildings. Among his ecclesiastical works the Cappella Lancelotti in San Giovanni Laterano, built on an oval plan with projecting columns, could be mentioned. The masterpiece of his mature style is Santa Maria in Campo Marzio (1682-85), an impressive Greek cross with oval dome but without drum. Still later he built the oval chapel in the Palazzo Monte de Pietà, amply decorated with reliefs, statues, and stuccoes. De' Rossi's elegant palaces, among them the Palazzo Altieri and the Palazzo Bonaparte, are important for the development of seventeenth-century civic architecture in Rome. //