He represented the Igunga constituency in Tabora Region from 1994 until his resignation in 2011. He was the ruling party Chama Cha Mapinduzi (CCM) National Treasurer from 2005-2007 and member of the Politburo/Central Committee of CCM from 2006 to 2011. Some of the key as an MP he pioneered community health insurance in East Africa and every household in his constituency was provided with health insurance from the Community Health Fund.He also achieved access to water for every resident in his constituency and Igunga Constituency became the first district to have a dispensary in every village and electricity in every ward.
According to Forbes magazine Rostam Aziz of Tanzania owns nearly 18% of Vodacom Tanzania, the country's largest mobile phone company, with 15 million subscribers. Rostam, via Cavalry Holdings, previously owned 35% of the company, but, in May 2014 he sold 17.2% of Vodacom Tanzania to Vodacom Group of South Africa for an estimated $250 million.
The Aziz’s are a fifth generation Tanzanian family of Iranian ancestry. They settled in Tanganika after transiting in Zanzibar, circa 1850. The family initially began farming sisal, rice and sugar cane.