Danny Harrison's double gave Rotherham a deserved win and consigned Dagenham to their third successive home defeat.
Harrison struck at the end of a forgettable first half, turning Stephen Brogan's cross home from four yards as Dag & Red's defence switched off.
The two combined once again after 51 minutes, as the unmarked Harrison volleyed home from the penalty spot.
The Millers almost extended but Marc Newsham's header was saved and Ryan Taylor somehow volleyed over the bar.
Dag & Red: Roberts, Foster , Uddin, Smith, Griffiths, Huke (Taiwo 70), Southam, Rainford, Strevens (Moore 63), Benson, Graham (Green 78).
Subs Not Used: Thompson, Boardman.
Rotherham: Warrington, Tonge, Sharps, Coughlan, Brogan, Danny Harrison, Mills (Hurst 85), Hudson, Newsham, O'Grady (Todd 85), Taylor.
Subs Not Used: Annerson, Peter Holmes, Yates.
Goals: Danny Harrison 45, 52.
Ref: Richard Beeby (Northamptonshire).