He could have saved him. He sat there for 2 minutes while they talked. You just want to believe that he couldn't save him because the alternative is that Batman killed him by omission. And that's uncomfortable because speaking against Nolan is a crime among Batfans.
He could have saved him. He didn't.
So Rachael can fall off a skyscraper and all he has to do is jump after her and grab her and use his cape to "sorta" break their fall onto a car but he can't grab Ras and jump out the back and "parachute" to safety?