Looking at it from a personal opinion standpoint, hell no.
Looking at it from a usefulness standpoint, hell no. Here's why.
In a roleplay, it usually requires the establishment of a bunch of things in the beginning (IE. Characters, sometimes plot (or at least the starting off), who's who, etc). If you do it in a channel, then every time someone comes in, you have to be like "Ok here's literally everything here's who's who and like here's yeah"
Plus if someone leaves it's really awkward because if the plot is around them at the point in the RP, you're pretty much killing an entire channel until they come back.
Plus, making it public allows people to just come in and be like "AND THEN A MONKEY CAME OUT AND LE POPED ON EVRI1 XDDDDDDDD"
In addition, when there are roleplay channels in other IRCs, there's generally one show/thing that the IRC is based upon. For instance, I was in an pony IRC and there was a pony RP channel. Because everyone there would agree that it would be about ponies. In a game like osu!, you'd go in and people would be like "I WANNA DO HETALIA XD" and someone else is like "I WANNA DO PONIES" and like there's no established guideline of what world the RP would be in. Multiple RPs don't work in there either, lol.
@Otonashi: That would get so intrusive, though. I do agree that a channel for anime/manga discussion would be nice, but people would wanna talk about a new episode of a show they like and people would be like "RUSSIA AND POLAND TOOK OFF EACH OTHER'S PANTS XDDDDDDD"
As an additional note, I've noticed often that separate channels to discuss individual topics have never really worked out as well as imagined. Look at how often there's large video game discussion in #videogames (The last I remember is when Mario Kart 7 was big, and E3 (Last year. My net died for this year's so I'm not sure)