My current dog, Brian, an Australian Shepherd, is only 14 weeks old, but I have no plans to allow him to run loose even though we live in a rural area. I had my Collie, Katie, and lived in the country for more than 10 years and even though she was totally trained, she was never allowed to run loose. There are just too many things that could go wrong, the LEAST of which was traffic. In the country there are hawks, venomous snakes, coyotes, and even mean humans who think nothing of hurting animals for the sheer sport of it. It's just not worth it. I would never forgive myself if my dog got hurt because I allowed it to run loose.
Ghilly
When you say "roam around freely" do you mean -just turned out to take themselves off for a walk and come back when they feel like it?
If so, then no, I don't think they should. What if they wandered onto a road and caused a road accident? What if they attacked a cat, worried sheep, chased cattle, or got into a fight with someone else's dog? (these things can happen even with a pretty good dog)
Or -what if they got hurt themselves? The owner wouldn't know where they were, wouldn't be able to help....etc Or in areas where there are hazards like coyotes, foxes, etc.
Actually I know a dog very well indeed who does this. The owners live near me. He is OK, as nowadays when he gets let out he comes down to my house and hangs out here which is fine with me. I look after him till I send him home, and I don't mind (oddly he goes STRAIGHT home when I tell him to!)
But no I would NOT advise letting a dog roam around on its own in the countryside.
However, if you mean "letting them run free while on a walk with you in the countryside" -then YES! But that's got to be a good dog who will come straight back when called or whistled.
I have met a number of scared and worried people hunting about for their dogs in the woods....just because they let them run off leash, and hadn't bothered to train them to return when called!
Actually, I don't live in the country but have taken my dogs out to these types of areas over the years. Even if I lived in the country, there is no way I would let my dogs run free due to too many hazards, them possibly running off, yada yada.