Debora Caterini, a 47-year-old teacher, and her daughter Aurora were buried in the rubble of the collapsed building following an explosion caused by a gas leak.
A man and a 68-year-old woman were seriously injured in the blast and transported by air ambulance to hospitals in the capital. Two other people were rescued.
The blast shook windows of nearby buildings.
"We had just finished eating and we heard a huge explosion," Rosalba Neri, who lives in the building opposite, told Il Messaggero.
"We thought a plane had crashed. Then we looked and saw the scene: the building was no longer there and all around were smashed windows, broken glass and damaged cars."
Rome Mayor Virginia Raggi met with relatives of the victims at the scene on via Giacomo della Marca on Wednesday evening.