There's a bug with "Rocker" & "Skull".
When a Lv.2 or higher "Skull" dies and spawns a lesser "Skull" it consumes one of the "Rocker" invincibility blessings but DOES NOT apply it to the "Skull".
I've tried it with every item and lane matching nothing fixed it.
Maybe worth noting if you give the "Skull" the item that makes it summon "Bones" when killed, the blessing WILL apply to the "Bones" but still NOT for the "Skull".
Playing on mobile, doubt that matters though.