The Millers paraded the Papa John’s Trophy they won last weekend prior to the match but the ones in a jubilant mood come the final whistle were the Londoners.
Rotherham are now three points shy of MK Dons in the automatic berths they have held for so long this season in their bid to make a quickfire return to the Championship – although they do have two games in hand over second place.
“We just were not at our best. Whether it’s after the Lord Mayor’s show or emotional fatigue, I don’t want to use that as an excuse,” said Warne.
“I am not sure we deserved to lose but I don’t know if we did enough to win. I thought our first half performance was okay.
“We looked like we were going to nick a goal. I thought if we got one, we’d go on and win handsomely, but it wasn’t the case and it is happening a few too many times at home at the moment.
“After they conceded we didn’t play well enough to get back into it.
“Realistically we haven’t worked their goalkeeper enough.”
George Dobson fired home the only goal of the game to give the visitors the spoils.
The Millers have the chance to provide an immediate response as they travel to Portsmouth to play one of their two games in hand tomorrow night.
Rotherham United: Johansson; Harding, Wood, Ihiekwe; Barlaser (Osei-Tutu 68); Ogbene, Rathbone (Lindsay 62),Wiles, Ferguson (Miller 62); Ladapo, Smith. Unused substitutes: Mattock, Kayode, Edmonds-Green, Chapman.
Charlton Athletic: MacGillivray; Clare, Pearce, Famewo; Matthews, Gilbey, Dobson, Morgan, Blackett-Taylor (Purrington 90), Washington, Stockley. Unused substitutes: Jaiyesimi, Forster-Caskey, John, Leko, Harness, Burstow.
Referee: R Joyce (Cleveland).