You need to take him off the perch, and bring him inside, say to your bathroom, and either put him in a crate or on a towel, near a heater. Immediately. Right away. Don't even take time to read the rest of this, just go! Put food and water where he can reach it. THEN come back and read the rest of this.
Now, watch very carefully for any poop. Update us with what it looks like. If he hasn't been eating, it will be very watery. If he's gone too long, it could start to turn bright green, which is emergency time. If his crop is empty, you need to get something in him. Immediately. Get some water with honey and ACV in it, at minimum, and dribble it over the top of his beak, out away from his nares [nasal openings], where it will run across the beak and into his mouth. He will almost certainly instinctively swallow. And keep trying until there's at least a tablespoon in him before you even give him a break.
Next, if you have baby vitamins with no iron, or powdered electrolyte & vitamin mix for animals, that needs in his water, next. Mix the electrolyte/vitamin powder into a bit of water until it is honey colored, and get that into him, same process as above. Or, if you have the baby vitamins, give him at least 2 or 3 drops, with the same method. As for his feed, soak that with the same blend of electrolyte/vitamin water mix, until it's a mush. That should help him digest it, if he will only try it. You might have to dip his beak into it a few times.
I never saw an answer about those pellets next to him in the picture. What were they?
Also, is there another rooster, or a very dominant hen?