San Mattia Apostolo is a modern parish church at Via Renato Fucini 285, north of the Via Nomentana in the east part of the district of Monte Sacro Alto. Picture of the church at Wikimedia Commons. 
As befits its period, it is a spectacular Brutalist design, in concrete, low and of one storey. The plan is of a half-open fan (except that the frontage is straight not curved), and the roof corresponds to this by having seven large ribs or vanes. It has a concave slope, descending slightly from the frontage and then ascending to the point of the fan above the altar. The ribs are actually double, made up of vertical concrete panels, and the gaps are bridged by glass. Thus there are seven strip-windows in the roof, which are symbolic of the seven sacraments.
The entrance has a double set of doors, each bounded by a pair of concrete slabs with sloping outer edges. The roof with its vanes continues over the entrance to serve as an unsupported canopy. The side walls are solid rough-cast concrete, and the altar end has the roof vanes coming together and supported by massive inwardly-sloping concrete pillars separated by vertical strip windows.
Inside, the floor is of high quality, using square blocks of porphyry in imitation of the cobbled streets of the Centro Storico. There is a bronze crucifix over the marble altar.
There is a parish website, but because of security issues with the server the hyperlink cannot be provided here. It can be found on the diocesan web-page.