[2] Roselan began his career with the Brunei Administrative Service (BAS) in 1985 at the Ministry of Finance (MoF).

In 2008, he briefly served as an Advisor to the executive director at the International Monetary Fund in Washington, D.C., before being appointed as Deputy Permanent Secretary (Policy & Administration) at the MoF.

[6] In April 2016, Roselan visited Singapore under the Ministry of Foreign Affairs' Distinguished Visitors Programme, engaging with Singaporean leaders and officials.

[7] On 15 September, Roselan underlined that the Bruneian government is dedicated to creating an environment that is favorable for investors and SMEs by streamlining procedures, expanding resource accessibility, and raising the ranking of ease of doing business.

[8][9] In March 2017, Roselan highlighted that, despite 92.8% of Brunei's civil service staff receiving high performance grades for 2016, there is still room for improvement.