If i rented, and I saw a sporadic rodent, I probably wouldn't raise it as a concern to the ll. If I saw a swarm of them, I'd suspect it's an infestation, and make sure to contact my landlord. Generally, as a renter, I would expect the landlord to at least make an attempt at dealing with a suspected "infestation", or if it really bothered me, I would ask my landlord to break whatever lease i still had and find another place to live.
I don't have a rodent problem, but I do seem to see a swarm of geckos where i live (please no insurance jokes). I generally don't mind them, because they tend to eat all the bugs. One made the unfortunate decision to sleep under one of my car's tires, and I sort of had to scrape the flatten remains off the garage floor. Another one met it's demise when it decided to sleep inside my wife's shoe and was squashed when she put the shoes on and went jogging. Funny thing is my wife didn't notice until I saw a flattened gecko on the carpet, apparently left after the gecko dislodged from her socks while walking in.
