Dear Hugh,
Glad to see the roofers are done. The problem with those nasty critters–those old galvanized roofing nails popping up like mushrooms on the ground–is easily solved. If your surrounding land is fairly flat, try this: 30 In. Magnetic Sweeper with Wheels. If the land around your home is rough-n-tumble (like mine) just get one of these on the end of a rope and drag it over, under, and around the home. I like this one, since it does “double duty” in my pond as well: 250 lb. Pull Retrieving Magnet. (Note: prices seem to change rapidly for these items on Amazon. Check before buying.)
Those old and usually rusty/corroded roofing nails are prime suspects for foot puncture wounds as well as wounds to our trusty K-9’s feet. (Don’t ask me how I found out about foot wounds; well, it was a 90-minute trip to the nearest ER for a tetanus shot.) Flats to the pickup and farm tractor tires just result in the dear spouse’s blistered ears. YMMV– try other sources, Amazon, Northern Tool, flea markets, et cetera. All the best! – K.W.