It probably says something about how little about the way the rats look seems to stop - or even bother Inigo. He just jumped right into fighting them, and even now as he's slashing more of them out of the way, he isn't even batting an eye. It's one of the benefits of having been forced to learn true combat experience in the middle of the zombie apocalypse - nothing is really gross anymore.

Not even fighting gross rats in a sewer.

But as he's still going at it, trying to find the areas where the rats mob together so it's easier to take out more at once with a swing of his sword, he can sure hear the odd sounds echoing from the sewer walls. The sounds are odd compared to the ones he's used to from home, the ones he's heard for years and years, and so after a moment he ends up calling out:

"Hey, what are you doing over there, Roland? You aren't cheating, are you?" He doesn't sound too serious about it though. If anything, the words sound borderline teasing.