If players /roll in raid, their realm name doesn’t show up in the output if they are on a different realm. This means that if 2 players have the same name on different realms in a cluster, they could be in the same raid and /roll for something and it wouldn’t be possible to distinguish their rolls from each other.
I suppose this assumes they are also the same class, or for some reason you don’t show class colors in your chat.
The rolls are sent as system messages. I don’t think it matters if they are the same class, but regardless this makes it impossible to determine who rolled what in these situations.