I am of the keep them in crowd, too. Mine went from prairie/ranch cats going in and out at will to being indoors all of the time for the rest of their lives and adjusted quite well. My current *crop* have always been inside, however they have a "chicken coop" we built up against the house. I open my office window, they go out on their "balcony", walk down a ramp and play in the grass, all within the safety of their 'coop." Keep us all happy. I never, ever want to find one of my cats dead on the road, again.
You can also buy commerical enclosures such as THESE and/or a mesh fence topper. Drs. Foster and Smith used to have them, but I couldn't find them, tonight. It's is secured to the top of your fence and juts out horizontally so that when the cat tries to climb over the fence it winds up butting the mesh with its forehead and can't get any further. At least that's the theory. I've never tried it as I figure my cats would find a loop hole somewhere in the fence or the topper.