Had similar problems and spent quite a bit of time working with an exterminator. He gave me the the following wisdom. Poison has the problems mentioned above. Also, it may lead to dead rats rotting in your house. If they die in your house, all their fleas and disease migrate off. Spring traps work well. As indicated earlier peanut butter makes a great bait. Smear it UNDER the trigger plate. Makes it more likely their neck is in the right place when the trap springs. Exterminator also put a peanut on the prong on top of the trap. Finally, he wore surgical gloves when he set/baited/handled the traps. Put traps adjacent to walls. Trigger plate goes closest to the wall.

Once they are gone (you haven't seen/heard/trapped any despite having 5-10 traps baited and out for two weeks) pull and replace all the gross insulation. It is full of stuff you don't want in your house and may attract others. Find/plug all entrances with hardware clothe or steel wool and spray foam.

Rats fear light and change. He recommended I string up LED lights in my attic and put them on a timer to go on for a bit every day. They don't like sudden light, feel uncomfortable and will likely not hang around.

Good luck. Did I mention that I HATE rats?