German minister to step down after vote setback - sources
Merkel was expected to make the announcement in a statement to the media scheduled for 4.30 pm (03:30 a.m. British time).
Roettgen, 46, was a Merkel protege and deputy chairman of her Christian Democrats (CDU) who had been seen as a potential successor to the chancellor.
He quit his party posts after taking responsibility for the CDU's worst ever election result in Germany's most populous state, North Rhine-Westphalia, on Sunday where he stood for state premier. The opposition Social Democrats (SPD) scored a resounding victory and retain power with their Green allies.
(Reporting by Markus Wacket; Writing by Stephen Brown)