Santa Maria del Rosario in Prati is a modern parish church with its postal address at Via Germanico 94 in the rione Prati, just south of the Ottaviani metro station. The main entrance is on the Via degli Scipioni to the north. Picture of the church at Wikimedia Commons. 
The remote ancestor of the parish is the little church of San Lazzaro on the slopes of Monte Mario, which had an enormous but thinly populated parish at the start of the 19th century. This included what is now the rione Prati, then nothing but countryside.
In 1838, the parish was transferred to the Dominican convent church of Santa Maria del Rosario a Monte Mario. However, after 1870 the Prati district was rapidly urbanized and the location of this church became very inconvenient. As a result, the Dominicans instigated a project to build a large new parish church in Prati to replace the convent church, but with the same dedication.
The church is in a Gothic Revival version of the neo-Romanesque style (round arches replaced with pointed ones).
It is a long, narrow building with nave and aisles and an integral three-sided apse. The roofs are pitched and tiled, and the external walls are in red brick with architectural details in white limestone.
The gabled façade has one storey, and the nave frontage is framed by two limestone pilasters without capitals rising from ground to roofline. Where the sloping aisle rooflines meet these is a pair of mosaic heraldic shields in decorated square frames.
The pointed-arched entrance has a tympanum containing a mosaic of Our Lady being crowned as Queen of Heaven. Doorway and tympanum are recessed, and are framed by four Corinthian orders, in turn (outside first): pilaster, column, pilaster, column. A raised string course runs across the façade at the level of the tops of the capitals. The outer pair of pilasters support a stone frame for the arch, which itself has a dentillated gable top. Above this is a spectacular wheel window containing stained glass, set in a dished frame. The sixteen radial mullions are miniature columns with capitals, and the dish frame is embellished with coloured mosaic in a quatrefoil design.
The ends of the aisles have Gothic windows over smaller side entrances. The windows are recessed in a similar style to the entrance, and have lancet tracery with four vertical lights each. The pilasters of the windows continue downwards to frame the doors, which is very incorrect in the context of the Gothic style. The string course of the façade intersects the windows at the tops of their pilaster capitals.
The rooflines have traceries of pendant Gothic arches on tiny corbels, below a dentillated cornice on the nave.
There is a campanile to the right of the apse, a square tower of two storeys with a tiled pyramidal cap. It is in red brick with stone pilasters up the corners, pendant Gothic relief arches below the roofline and the dividing cornice and two-light Gothic tracery in the sound-holes.
The rich interior has a high narrow nave and two aisles, the roof of the nave having a Gothic cross-vault.
The arcades have Gothic arches with polychrome clustered columns, horizontally broadly banded in orange and white. The inner sides of these columns are continued up the nave walls to support the vault springers, meaning that the column capitals are split. The vaults themselves have polychrome decoration by Giovanni Battista Conti.
The altar has a triptych depicting Our Lady of the Rosary, and in the round apse there are three tall lancet stained glass windows. Another single-light Gothic stained glass window is in each bay of the nave walls. The overall effect is rather French.