The Italian was left baffled by the referee's decision to send off the centre-back, but praised his side's character for coming from behind to salvage a draw with 10 men
Oriol Riera headed home to give the Basque hosts an early lead and he doubled the advantage on 39 minutes, before the defender was sent off for the 18th time in his career.
Isco pulled a goal back on the stroke of half-time and Pepe brought Ancelotti's men level with 10 minutes left on the clock moments after Osasuna were also reduced to 10 men.
The Italian coach was baffled by Ramos' red card, but stressed his team showed patches of brilliance and praised their comeback at El Sadar.
"I do not like to talk about refereeing decisions," Ancelotti told reporters. "But it's a difficult decision to understand. The first is not a fault. I don't know, I don't know...
"We lost control after the goal, but the first 20 minutes were very good. It's amazing that the game went to 2-0 and we were reduced to 10 men after starting so well.
"The reaction of the team was very good, though - the team showed a lot of character and attitude not to lose."
Real Madrid sit two points behind Liga leaders Barcelona and second-placed Atletico Madrid following the game, but both sides have a game in hand.