After attending PGGMB School, Ruzaini continued his education at St. Andrew's School till 1996. He graduated from the University of Surrey in 2003 with a Certificate of Higher Education in economics and from the Coventry University in England in 2005 with a Bachelor of Arts degree with honors in economics.^[1]

In 2006, Ruzaini started working for the Government of Brunei as a marketing officer in the Civil Aviation Department of the Ministry of Communications. Since 2009, he has been employed by the Prime Minister's Office (JPM) in the Economics and Financial Development and Planning Division as a Special Duties Officer. He has taken part in several conferences and classes, including "Maximising Non-Aeronautical Revenue for Airports" in Singapore, "Achieving World Class Service Culture" at the IPA, "Maximising Non-Aeronautical Revenue" for Airports in Malaysia, and a working visit to the Civil Authority, Singapore and Malaysian Civil Aviation Department, among others.^[1]

In addition to these positions, Ruzaini held the following positions while employed by the Civil Aviation Department: Secretary to the Working Committee of Customer Day at the department; Member of the Committee for Arrival and Departure (Airport); Liaison Officer for the 6th Asean Telmin; Head of Secretariat for Communication Committee, Brunei International Airport; and Royal Wedding Ceremonies of Princess Majeedah Nuurul Bolkiah, among others. He also attended a number of meetings while working at the Prime Minister's Office, such as the 19th ASEAN Summit in Bali, the 16th AFA Conference in Brunei, APEC – "Enforcing Contract, Ease of Doing Business" in South Korea, "Perfecting Key Performance Indicators," and the ASEAN-OECD Investment Policy Conference.^[1]

In 2009, Ruzaini was chosen to serve on the "Task Force Prime Minister's Corporation" committee. In addition, he has held a number of other positions, such as Member of the Foreign Direct Investment Secretariat and Secretary to address payment delays in order to increase government revenue receipts and raise the Global Competitive Index (GCI).^[1]

Since 2012, Ruzaini has been seen accompanying his wife, Princess Hafizah Sururul Bolkiah, to national events and celebrations, such as the opening of Brunei's ASEAN regional hub in October 2019,^[2] Hari Raya celebration in May 2022,^[3] and the "Family Harmony Festival" in November 2023.^[4]

On 20 September 2012, Princess Hafizah, 32, who is the fifth child of the Sultan and his wife, Queen Saleha, and her groom, Ruzaini, 29, exchanged vows in front of a large group of family members, friends, royals, and leaders from across the world, at Istana Nurul Iman.^[5][6] On the 23rd, the pair will be formally introduced to the royal court in a ceremony that would culminate over a week of wedding-related activities.^[7][8][9] That evening, the newlyweds in the Islamic sultanate would be honoured with a royal banquet attended by leaders of Southeast Asia and international aristocracy.^[10] Present at the wedding is Najib Razak,^[11] Rosmah Mansor,^[12] Yingluck Shinawatra, Benigno Aquino III, Hun Sen,^[11] K. Shanmugam, Musa Aman and Abdul Taib Mahmud were among the ASEAN leaders in attendance.^[13]

After his marriage, he was given the title of Pengiran Anak, and styled as Yang Amat Mulia (His Highness).^[14] The couple have 4 children:^[15]

In the family of Dayang Hajah Zainon binti Dato Paduka Haji Elias and Dr. Haji Mohd Yakub bin Pengiran Haji Othman, Ruzaini is the second of five siblings. Pengiran Muhammad Afizan is a businessman and his older brother. Among his siblings are Awangku Muhammad Tarmizi, a student at Coventry University in England; Dayangku Dr. Amalina, a medical officer in the Ministry of Health; and Dayangku Amal Aqilah, a legal officer in the Ministry of Finance.^[1]