So I have never played one, but the thing I read somewhere is that early RockBasses did not used to carry Warwick’s branding with the logo, and the general opinion is there were serious quality control issues with them. Eventually Warwick clamped down on the quality issues and once satisfactory started putting their logo on them. I do not have a reference for this though.
Another thing to point out is that some of the older non-W RockBasses did not have the two-piece bridge. You absolutely want the two-piece bridge; you absolutely want the Just-A-Nut as well. Warwick’s adjustable bridge system and the adjustable nut are two of the best things about them. The bridge should look like this:
and not a normal one-piece bridge. The nut should be similarly adjustable via two allen bolts as well. As far as I am concerned those are table stakes for considering an older Warwick of any kind, not just the RockBasses.
I would personally not consider a non-W RockBass. That said I have owned two Warwick branded RockBasses and they were both fine.