i can hardly believe a skunk would kill a rooster. was he roosting on the ground? i have never known a skunk to kill an adult bird. first off it would have trouble catching one. and they don't climb, they will dig under fences but will not climb over.
i've watched a skunk catch & kill a full grown and fighting RIR rooster, at dusk and with our two labs going NUTS barking at it.
I had been losing birds during the early light/dusk hours, but couldn't figure out what was getting them...turned out, it was the skunk that killed my rooster. i free range my flock during the day, but they are closed up in a coop at night.
my birds were going to roost in their coop, and the skunk was waiting at the door to the coop. as Scrappy the Roo walked in, it reared up on it's back legs and "grabbed" Scrappy around the neck, sinking it's teeth into the back of his neck. Scrappy blasted off, fighting for all he was worth, but in literally about 45 seconds he was dead, neck broken & almost bitten through. I grabbed the shovel we keep at the door for snakes, etc. and ran over, and was so mad that I killed the skunk with one whack, before it could spray. it didn't even see me coming, it was so busy with eating Scrappy's croup out.
so they can definitely kill roosters, and big strong ones at that!