C.O.
I would be VERY concerned if my dog ate a dead rodent. Especially since you don't know how they died. I would not be happy if my dog got poisoned by ingesting them and the poison they ate/consumed - even if they are small.
I would contact Terminix or some other pest control company to find out how to deal with them.
As to the snakes? Are they just plain old garden snakes or what? snakes EAT the rodents....you know - the food chain? I would want them around to deal with the rodents!! :) I know - not ideal - but I would wonder and ask around the community what has caused the influx or rise in population of the rodents and snakes. You can usually trace it back to something....a building...a new construction project over once deserted land....
GOOD LUCK!!