[9] As secretary to the cabinet under the Raykov Government, Zhelyazkov was implicated in the so-called "Kostinbrod affair" surrounding the 2013 Bulgarian parliamentary election.

A number of political parties, most notably the BSP, alleged that around 350,000 ballots were printed illegally at a facility in Kostinbrod with the authorisation of the caretaker government.

[5][6][4][13] In this role, he helped draft legislation for the implementation of e-government in Bulgaria and represented the country at the annual summit for open government partnership.

[22] In November 2018, Zhelyazkov announced a change in the leadership of the Bulgarian State Railways after a number of allegations of misappropriation of funds, as well as a lack of communication with the Transport Minister.

[25] Another challenge faced by Zhelyazkov were allegations by the Bulgarian Socialist Party that the contract for the concession of Sofia Airport was contrary to European legal practices due to undue favouritism towards a private company.

[29] In February 2019, the bus drivers' union of Bulgaria threatened to hold a national strike due to unclear regulations surrounding the distribution of state subsidies to the sector.

[30] In an interview with bTV, Zhelyazkov admitted that widespread corruption remained a key problem in the "Automobile administration" department, and promised to address its "structural" causes.

[38] As part of the government's efforts to combat the economic impacts of the COVID-19, Zhelyazkov authorised the implementation of the 60/40 wage scheme within the transport sector.

[6] On April 19, 2023, following an agreement between GERB-UDF and the second largest group in the National Assembly - PP-DB, Rossen Zhelyazkov was elected Parliament Chair with 136 votes in favour.

[41] On 1 July, Zhelyazkov was asked to form a minority government as prime minister by President Rumen Radev following the June 2024 Bulgarian parliamentary election.