I just wrote this on another thread, maybe this helps....
So this website has a specific forum for it here.
https://www.backyardchickens.com/forums/animals-in-need-of-free-re-homing.16182/
I am guessing that this will work better if you are in a populated area, because it will be more likely that other BYC members will also live there.
I have used craigslist with pretty great results. That seems to work better in rural areas since there are usually more folks looking for roosters, but not always.
There is something called Front Porch Forum in Vermont, which is basically a listserve for each town to post announcements. I have actually had people pay me for roosters on there, just $5-10, but still something.
That is just for Vermont, but there are some other neighborhood forums I have heard of (like nextdoor.com). Maybe a web search for "neighborhood forums in [wherever you live]" may yield some results.
It is so sad to have send a rooster away, literally or metaphorically, but I comfort myself by knowing that they had a great life with me, even if they were only with me till I found out they were a rooster. Also, some of them are better off anywhere else than in a flock with multiple roosters with a lot of fighting an hardship. I try to remind myself of that in those hard moments.
Good luck!