Southend booked a place in the FA Cup fourth round with a comfortable win.
The hosts took the lead when Dean Morgan's cross was stabbed home by Charlie MacDonald but Jon Nurse and Ben Strevens turned it around by the hour.
Matt Harrold teed up Morgan to blast in the leveller from just outside the box and Simon Francis rifled home through a crowded box to put Southend back ahead.
Daggers keeper Roberts was sent off for a clash with Peter Clarke before Nick Bailey and Morgan netted from close in.
Southend: Flahavan, Hunt, Clarke, Barrett, Hammell, Francis, Bailey, McCormack, Morgan, MacDonald, Harrold (Hooper 77).
Subs Not Used: Collis, Black, Moussa, Herd.
Goals: MacDonald 11, Morgan 64, Francis 77, Bailey 90, Morgan 90.
Dag & Red: Roberts, Foster, Uddin (Smith 30), Boardman, Griffiths, Saunders (Thompson 87), Huke, Southam, Sloma (Taylor 80), Strevens, Nurse.
Subs Not Used: Rainford, Green.
Sent Off: Roberts (87).
Booked: Griffiths, Boardman.
Goals: Nurse 32, Strevens 58.
Ref: Tony Bates (Staffordshire).
BBC Sport Player Rater man of the match: Southend's Adam Barrett 10.00 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.