My rooster did the same thing. I thought he was a goner as his head was lolling to the side and he couldn't stand. I picked him up, sure he was going to die in my arms and remembered some good advice from BYC. I wet his feet and his comb, shoved some yogurt in his mouth; I re-wetted the same areas and took him out of the coop. I put him in the wheelbarrow with some hay, water and more yogurt and held my breath.
By next AM, I was so sure he'd be gone but he had his head up...not standing. Long story short, he's fine now. Unfortunately, the other roosters wouldn't accept him back in the coop so he has his own place along with an aging hen. They're both doing well and Fred, the rooster, is crowing happily again.
The trick is to find them before it's too late. Being too late can happen quickly in South Texas.....
Good luck.