Personally for me I would hold off on Rollins returning until at least SummerSlam 2016 and then after that I would still pair him up with The Authority but also I would build towards Triple H/Rollins for WrestleMania 33 that is just what I would do anyway to build Rollins back up to become a babyface but by him re-aligning himself with The Authority first staying as a heel for the first few months but then have him show signs of becoming a babyface or making that transition where then you could have him turn on Triple H and Stephanie or you could have them turn on Rollins
Not really. He gets too many cheers, and his moveset fits a face so well. He's so beloved by fans (adult smart fans) that when he returns it'll definitely be as a face.
As for the OP, it's looking like Summerslam, which would be great and much more impactful.
SummerSlam would be more ideal but if they wanted to take him off of TV for a whole year then the Royal Rumble would be a perfect place for him to return and then surprise everyone in the 30 man Royal Rumble Match and then win it in his return
It'll be cool to see him in May, but I am a fan of Roman Reigns as a champion and Dean Ambrose. I want to see them go at it at Mania 33 more than anything else.