You take precautions for him not to get tangled up, that's how.
Most tie cords I've seen have a swivel on the stake end and as long as long blades of grasses, sticks, and such don't get wrapped up in it, the rooster stays tangle free.
I use tie cords with stakes, staked into the ground, gives him a good 16ft circle of space to live in. He has a barrel to roost on or in, whichever he prefers, and a waterer placed at the edge of his range where he can drink from it, but not knock it over. The barrel is also placed so that he can't walk all the way around it. Food is tossed on the ground for him to eat at feeding time.
I've also seen barrels with cords attached from the top, and some that have cords attached near the opening at the bottom cutout.