You can see where that failure initiated in the lower left corner of the roller side, a slow ductile fatigue like thing, propagated across that side all the way to the little pedestal left on the top side then went into brittle failure. Note that the rod side is a full brittle (high speed) fracture. Amazing how long it held together before catastrophic failure. Even a small ding along that edge started the process who knows when. This is a main reason for deburring edges of machined parts, not just a cosmetic thing.
Load side bearing surface wear is also kind of neat to see as opposed to the top side.