The league leading O's will check on Kevin Lisbie ahead of the visit of the Millers.
The 11-goal top scorer was forced to sit out Tuesday night's 3-1 defeat by Coventry - their first loss of the season - with bone bruising in his leg and boss Russell Slade rates him as 50/50 to return.
Shaun Batt will continue in attack alongside David Mooney if Lisbie is ruled out again.
Slade has no other major injury concerns and could hand a debut to midfielder Frankie Sutherland following his recent loan switch from QPR.
Rotherham are able to welcome back a number of players for the trip.
The Millers were missing suspended duo Lee Frecklington and Michael O'Connor for Tuesday's 1-1 draw with Tranmere while Michael Tidser and Kari Arnason pulled out on the day of the game with illness.
Frecklington, O'Connor and Tidser, who did make the bench, will definitely be in the squad but Iceland international Arnason is still being monitored.
Claude Davis (hamstring) and David Worrall (groin) remain missing as Steve Evans' men look for a first win in four League One games.