What is a 0wt really anyway? There aren't AFTMA standards for lines below 2wt, only manufacturer (Sage, basically) "conventions" so there is little consistency. When you see rods at 0wt or 1wt or 0000wt or 2wt about all you can safely assume is that the rodmaker decided they were lighter than a 3wt
That said I have an RDP 7'6" 0wt that I bought from a forum member here a few years back for far far too little money. It is a superb rod, I love it and fish it all the time, certainly for things it was not meant to do. I abuse the crap out of it. I broke the reel seat off and epoxied it back on. At some point the tip section broke and the new one has different sized guides and different guide spacing and different thread color so it looks real janky.
I couldn't tell you its true line rating as I find that to be fairly subjective. I will say that I typically use a 1wt line with it, mostly because I have several of those and they are cheap. I have used a 2wt in a pinch and it cast it great over short distances but got overloaded before the whole head was out. I have never held a 0wt line and I am skeptical that there are any commercially available at the moment, marketing aside. If there were, I am certain this rod would cast it fine.
As further testament I later built an RDP 7'6" 1wt, and then an RDP 9'0" 5wt. RDP isn't compensating me for this extensive free marketing but perhaps they should -- Mark, get in touch