Madjo's 56th-minute strike cancelled out efforts from Gareth Evans and Sam Hoskins who had twice put the Millers ahead before the break, either side of a Peter Vincenti goal for the home side.
A point was no good for either side - who both finished with 10 men after Millers defender Tom Newey and Shots substitute Jordan Roberts saw red.
A dominant Rotherham went in front after 11 minutes - Evans scoring from the spot after being brought down by Darren Jones.
The Shots levelled nine minutes later when Vincenti reacted fastest to Madjo's parried shot to prod home from six yards.
Rotherham led at the interval after Hoskins fired into the top corner but things were level again when Madjo's header found the back of the net.