You have to remember, Rollins got a lot of flack from Foley for interference. So, it makes sense.
I thought the same thing as everyone else, is this a stepping stone for a storyline involving Shield's return?
I disagree. Rollins is not less likely to interfere in a match just because Foley gave him flack for it. In fact, I would say he was more likely to interfere for that very reason.
But even if that was the reason, Rollins could have then gotten involved immediately after the end of the match. He didn't. He waited all the way until both KO and Jericho got Reigns back into the ring and were attacking him. If he simply wanted to attack KO and did not want to interfere in the match, the moment both Reigns and KO hit the floor, he would have come in and done his attack. He didn't do this. He waited. So it doesn't appear that he was trying just not to interfere, it appears clearly that he was trying to save Reigns.