Chicken longevity

Question; Is there a general health regimine to help my rooster and chickens live long productive lives?

Background; I have had a backyard flock for about 7 years with my current oldest bird 4 years old, my Rhode Island Red rooster. He is great and would like to keep him healthy for many more years.
There are 11 hens and 1 roo and they all free range on 1/8th acre. I give food also, just a general layer pellet.
Free choice of oyster shell, about 4 cups scratch feed every few days, about two cups of dried meal worms about once a week, and 3 cups of sunflower seed a week.

Anything else I should be doing?

Roosters have longer useful lives than hens - yours should be good for possibly another four years.  Mainly, as long as they don’t get sick, and you are able to keep them safe from predators, it sounds like you are doing fine.  Maybe plant some comfrey if you don’t have any yet.

There is comfrey in the yard that they keep pretty well mowed down.
Anything else I could add to the yard?

Best perennial chicken feed thread: https://permies.com/t/997/perennial-chicken-feed  
If Mulberry isn't invasive in your ecosystem, it is frequently recommended because it produces fruit over a long season.
Things that attract bugs and worms - chickens are omnivores with a great affinity to being insectivores!

I’ve seen an idea in books that I have yet to try - plant nutritious perennials such as comfrey, alfalfa, and others in wide rows, and cover with an arch (low ‘hoop-house’) of chicken wire.  That protects the plants from being killed by the chickens, while allowing them access to the parts of the plant that they can reach through the wire.  You would need to support chicken wire with something sturdy or they would mash it down.  Or use sturdier wire, such as that used for building rabbit cages.  These structures might be two feet wide and high, and as long as you want to make them.

It sounds like you're doing a great job already, to be honest. All our chickens succumbed to predators rather than old age, especially on those lazy days when the person(s) responsible for closing the hatch either didn't make sure the hens were all in first, or took their time shutting the hatch after dark. Birds with clean, safe homes that get to forage tend to be pretty healthy.

Given the cards you have been dealt, I don't see how you can make significant improvements.