I have a wall mounted feeder in my juvenile coop/run setup. It is an old section of rain gutter that i repurposed. Its covered by a smsll section of roof to keep it dry. I would imagine that it is prone to rodents, but I have never seen one or sign of any.
My free range adults have a supplemental feeder in their coop. It is just a gravity fed feeder meant for cats and holds about 10lbs. I have an elevated coop and have never had a rodent issue.
We live in the mountains and are surrounded by fields and forest. There is no shortage of predators, scavengers, and theives that would love the free meal but none have been successful.