Waving hello from outside of Townsend MT <G>.
All I can offer is my recent experience. My youngsters [3 barred rocks and 3 EE including one that is hoped to be a roo] are 7-9 weeks old, the big girls [a buff orp, 2 EE and a bantam] are 13-14 months old and free range at will.
About a month ago the littles went out to the grow-out coop/run. They were secure, had their own food and water and a place to roost overnight. For the first few days the big girls were curious, watched through the sides, made no aggressive moves.
After a good growth spurt I started letting the littles out for an hour at a time. The older girls were interested but that's all. The outdoors time was gradually expanded. I watched to see that they knew where "home" was.
At this point, everyone gets let out when day begins here. They are all excited to the same degree. Each day the younger ones expand their territory a bit. The older girls will go in the chickies' run and eat their crumble, everyone shares the multiple waterers. (I'm looking forward to getting everyone on All Flock!)
The Buff gestures at any younger who comes near while she is eating. It is not violent, just an assertion, respected by the younger bird.
The younger girls will hang out in the main run but still go to their coop to roost.
So far the two groups will overlap but still seem distinct. They are sharing spaces, sharing feeders, mingling. It might be different for you with only 2 newbies.
Once our coop addition is complete and the younger girls are same size as the hens they will get put in that coop at roosting time. I expect them to fully integrate then.
My advice, based only on my experience is to start letting your barred rocks out into the main run, leaving them access to their secure place. Watch them but don't interfere as everyone gets oriented to the larger group.
As for how far anyone wanders: We have over 13 hilly acres with 80 acres of BLM at one fence line and a county road at the other with just a short run of fence adjoining another private property (it's an oddly shaped parcel). The chickens stay reasonably close to the house. They like the garden beds, going under the deck and juniper trees and are absolutely tuned into their nesting boxes and coop.
They have two dogs and a cat keeping track of them. So far nobody seems to get out of range. We do not have neighbors or stray dogs and are high and dry so no raccoons. The aerial predators have an ample food supply and are easily deterred by the dogs. Likewise for the coyotes.
Good luck! It's all an adventure.