Commissioner in Palestine in August 1870, at the time of the interreligious conflicts, he returned as consul of Alexandria in June 1872 after being placed on leave during the events of September 1870.
[5] But the task ahead for Roustan was enormous: the English took advantage of France's weakening following the defeat in the 1870 Franco-Prussian War to obtain numerous concessions from the reigning monarch, Sadok Bey.
Faced with such incompetence, he was urgently called back to Paris and replaced by Roustan, who had the difficult task of making people forget this whole series of failures.
The International Finance Commission, which managed the regency's tax revenues, was headed by a French financial inspector, Victor Villet and then Édouard Le Blant.
They appreciated the Tunisian government's desire to consolidate its finances and lent it their full assistance with the support of Roustan, who thus succeeded in reducing the influence of the British consul.
[10] The loss of Richard Wood's support was felt even in the economic performance of the English companies benefiting from the concessions at the beginning of the decade.
This was done on 7 May 1877 after the French government had granted its guarantee to the Compagnie des chemins de fer Bône-Guelma responsible for the works and created specially for the occasion.
But Kheireddine was no fool: the concession stopped forty kilometres from the Algeria-Tunisia border and he strongly rejected all French requests for an extension to their neighbouring colony.
[12] Kheireddine's desire to foster a rapprochement between Tunisia and the Ottoman Empire persuaded Roustan that the Grand vizier was an obstacle to the French predominance that he was trying to impose in the country.
Upon his return from the conference, the French Minister of Foreign Affairs, William Henry Waddington, asked the consul to prepare a draft of a "friendly" protectorate to be presented to the Bey of Tunis.
[15] Waddington eventually abandoned his project, aware that the French were thinking only of a revenge on the German Empire and not of a distant conquest which, moreover, would anger the country with Italy, animated by neighbouring ambitions.
Ferdinand Veillet-Devaux, so-called Count of Sancy, had obtained in 1866 a 1,200 hectare concession in Sidi Thabet to build a stud farm.
Faced with the refusal of the French consul then in Tunis, Viscount Charles Vallat, to support his abusive claims, he appealed to his brother-in-law, général du Barail, then minister of War.
Faced with such pressure, Kheireddine gave in and signed a new concession with De Sancy on 9 July 1877, granting him 3,000 hectares, on condition that he build a stud farm within a year.
Faced with demands that were known to be unacceptable, the French government was preparing for the breakdown of diplomatic relations, which would justify military intervention and the establishment of the protectorate.
[20] Faced with Sadok Bey's obstinacy to defend the regency's independence, Roustan convinced Mustapha Ben Ismaïl to use the monarch's weaknesses against him to get him to sign the protectorate treaty.
But it was a failure as he testified to Felix Desprez: "Mustapha remembers the anger of the bey who went without speaking to him last year for three days because he had advised His Highness to sign the treaty.
"[21] Failing to achieve his goals with the Tunisian monarch, Roustan recorded a small satisfaction when he finally obtained, on 31 March 1879, the recall of the English consul, Richard Wood, who had never stopped opposing his manoeuvres.
Roustan was then encouraged to accelerate the economic penetration of French companies by asking for the concession of a port at Radès and a railway line connecting it to Tunis.
When he left Tunisia, no Tunisian buyer being interested, he sold the property to the Société Marseillaise de Crédit, which had already acquired the estate of Sidi Thabet.
To this end, he bribed the Tunis consul in Annaba, Joseph Allegro, who informed him about everything that was happening in the border region to the point of boasting that he could annex this part of the country as soon as he was asked.
On the contrary, his links with Sadok Bey were highly appreciated since he succeeded in convincing the monarch to accede to French requests to involve the Tunisian Beylical Army [fr] in the repression of the insurrection.
In 1880, his liaison with the wife of the Tunisian government's Deputy Director of Foreign Affairs, Elias Mussalli, was extensively commented in the context of accusations of prevarication.