The German was forced to retire 13 laps in at the Marina Bay Street Circuit having started from second spot on the grid, and Rosberg's poor fortune combined with team-mate Lewis Hamilton's win saw the Briton take the drivers' standings lead.
Having previously attributed "reliability" to Rosberg's second retirement in six races, Mercedes released a statement claiming their system was contaminated by a substance that is used in servicing the vehicles.
The substance caused an electronics short circuit, and gave Rosberg no control over the clutch or the engine's settings.
"Forensic analysis has revealed that the steering column electronic circuits were contaminated with a foreign substance," the statement read.
"Fresh parts will be used at the forthcoming races.
"The team has been working intensively on reliability and quality processes during 2013 and 2014 in order to improve our performance in this area and these efforts will continue at the same intensive level over the coming months."