Lisbie struck in the 27th minute when he stabbed the ball into the net from close range after Millers goalkeeper Adam Collin had blocked a shot by Dean Cox and then pushed the midfielder's follow-up effort onto the crossbar.
It was the striker's 12th goal of the season, but O's boss Slade emphasised the value of whole of the team performance.
"The game demonstrated not only how important Kevin Lisbie is to the team, but how important everyone is," he said.
"We had to defend stoutly at times and all the lads across the back were superb.
"I can't actually recall a clear-cut opening that Rotherham had against us and that's how well we defended against what is a decent side pushing for a top-six slot.
"In the last 10 minutes, we were looking for a second goal just to give us a bit of comfort, it was a little bit nervy, but I thought we saw the game out well.
"We are doing things right at the moment and we just need to keep that momentum going.
"The game at times was a little bit scrappy but we were resolute. Sometimes the result is more important than the style."
Rotherham worked hard in the second half and enjoyed the greater possession without troubling O's keeper Jamie Jones.
It was left to Collin to keep his side in the game as he pulled off three saves to frustrate the home side and ensure a nervy last few minutes.
Slade revealed that star striker Lisbie only declared himself fit on Friday having missed the midweek defeat to Coventry through injury.
"He was in doubt right up to Friday," Slade added. "He was really only 50-50, but he put himself up and got the all-important goal for us. He's a great lad and a great professional. "