BTW. Make sure that the new “…-iso8859-2” fonts are really installed, before you introduce them in your “.rootrc” or “${ROOTSYS}/etc/system.rootrc” files. Just see what fonts are installed on your system using “xlsfonts”, for example.
Well you are welcome to try … but you should to it for the screen, SVG, PS, PDF, Etc … All these guys have different way to deal with text.
We are now in contact with somebody who reimplemented a new Latex interpretor for ROOT. I saw he was able to do chinese too. But that’s a bit early to announce it because this person is very busy and his work is not complete (PDF is missing). So we are perfectly aware of this request and it is in our to-do list.
I’ve just tried to change all “Gui.*Font” settings (and I’ve also tried to disable the usage of TTF fonts).
This didn’t help on my system.
Something somewhere in ROOT still know is better that I am to use iso8859-1 encoding when drawing in TCanvas.
It seems that none of this options affects drawing, only menus, etc. It would be really a shame if to obtain national characters we had only to change the font, which is unchangable now 
Font family, size, etc. depends on “Graphics” style in the notebook stylesheet.
CurrentValue[{StyleDefinitions, "Graphics", "FontSize"}]
(* 10 *)
CurrentValue[{StyleDefinitions, "Graphics", "FontFamily"}]
(* "Times" *)
You can manually change it: open Format->Edit Stylesheet…, add ```
Cell[StyleData[“Graphics”],FontSize->20]
and press Ctrl+Shift+E. You will see that here the font in Plot , LinePlot , etc. instantly increase.
Edit: default values for Plot , ListPlot , etc. separately can be set by
SetOptions[Plot, BaseStyle -> {FontFamily -> "Helvetica", FontSize -> 16}]