From 1924 until 1932 he was a technical consultant of the Ministry of Foreign Affairs (MAE), erecting, modifying or restructuring a great number of Italian embassies, legations, consulates, culture institutes and schools in Europe, Africa and the Americas.

[3] The most important works among the many which he designed in Rhodes city are: the Palazzo del Governo (today the prefecture building) built in 1926, in Venetian Gothic style, with a white and pink stone façade, resembling the Doge's Palace in Venice; the neo-Renaissance post office building of 1927; the Catholic cathedral of Saint John of the Knights (now Evangelismos Greek orthodox church), rebuilt among great quarrels in 1924–25, whose plans were reconstructed using engravings of the Church of St John of the Collachium, located within the walled city and destroyed in 1856; the Grande Albergo delle Rose, now Casino Rhodos, built with Michele Platania, but "cleansed" of all its deco embellishments in the late 1930s by Governor Cesare Maria de Vecchi; above all, the Mercato nuovo (Nea Agora, "New Market"), the center of the new city, an irregular polygonal structure enclosing the fishmongers pavilion, which possesses an unquestionable Oriental style.

[3] The quarrel ended in 1927 with a legal dispute, where Di Fausto showed that during his service in the Dodecanese he had designed no less than fifty buildings—houses, public buildings, churches, barracks, markets, schools—thirty two of them already built or in construction in 1927.

[7] At the same time Di Fausto, whose prolificity was impressive, was continuing also his work in Italy, above all in Rome—where he owned a thriving studio—and surrounding regions, where, in the second half of the twenties, he designed several housing complexes: among them, those for the civil servants of the MAE, in Via delle tre Madonne, characterized by its Roman barocchetto style.

[3][5] In 1926–28 he designed on the hill of Montelarice near Loreto the villa of the famous tenor Beniamino Gigli, a pretentious and luxurious mansion, whose interest lies in its plan with a central body and two tilted lower wings, a concept that Di Fausto would re-use several times in the future.

[5] On 21 February 1930 he had a bad airplane accident in the northern Tyrrhenian Sea, being rescued together with his crew after 12 hours by the ship Citta' di Tripoli.

[8] The latter complex, placed in scenic position in a pine wood in front of the sea and near the ruins of the Villa of Nero, is a good example of Italian rationalism.

[3] Here is particularly noteworthy the chirurgic tuberculosis pavilion, with a central body containing the operation room, whose semicircular outer wall is a single glass façade.

[8] The dairy in Pescara, also demolished ın 2010 amidst much controversy and legal fıghts, was a three-body building upholstered with Clinker, whose central body façade had a treble glass wall.

[3] In 1932, Di Fausto became "consultant for architecture" of the city of Tripoli, the capital of Italian Libya, beginning the last creative phase of his professional life.

[3] In 1934, the replacement of Pietro Badoglio with Italo Balbo, the brilliant and impetuous Ras of Ferrara and Maresciallo dell'Aria, as Governor-General of Libya, boosted his work.

[10] On 15 March 1937, with a lavish night ceremony in the presence of Mussolini, the Arch of the Philaeni near Ra's Lanuf was inaugurated, marking the border between Tripolitania and Cyrenaica along the newly built Via Balbia (today's Libyan Coastal Highway).

[10] His position as Balbo's "court architect" was sealed by the placement of his portrait near the Governor's in the frescoes painted by the Ferrarese Achille Funi on the vaults of the Church of Saint Francis in Tripoli, another work of him.

[10] In 1940, Di Fausto took also a short detour from his main activity, designing the scenography of the historic movie The King's Jester (Italian: Il re si diverte), directed by Mario Bonnard.

[3] His most noteworthy works during those years were the plan for the post-war reconstruction of Subiaco, the restoration of the cathedral of Sant'Andrea Apostolo of the same town, the design of the General House of the Cistercians on the Aventine Hill in Rome, and the restructuring of the Sanctuary of Montevergine, built in an arid neo-Romanesque style.