After my dog got into some warfarin set out for rats and needed a $1000+ blood transfusion and almost died, I'm really cautious about using poisons. Plus, rats around my city are so used to the dang stuff (it's utterly ubiquitous) they've got immunities to it or else know to avoid it.
For my coop I put fine gauge chicken wire ALL around it and over the top of it so it is COMPLETELY sealed. I also BURIED the chicken wire at the bottom and dug a trench around the perimeter of the coop and buried scrunched up chicken wire in that. I don't have my birds in their coop yet. Hope to have it completely constructed by the end of the weekend.
Other than that, I know that there are rats in a pile of yard debris by my bike shed. I'm removing that, plugging up the holes near the foundation of my house they've been using to occasionally sneak in, and making my yard as uninviting to rats as possible.
Rats, raccoons, skunks, dogs and cats are all on my mind as I construct my coop/run. I'm not sure that the chicken wire I'm using along the run is strong enough to keep things from chewing through it. If they do, it would be pretty scratchy to go through and I'd patch it up/put another layer around. Gotta protect the babies!
To sum up: I don't think poison is your only option and I've encountered problems with it. Maybe if you're not in a city, your rats will be more susceptible to poisons. The only thing I've found effective is keeping the food inaccessible to rats to the best of your ability and eliminating their points of entry. This is a long term/safe solution where poison is a short term/dangerous one.