I don't remember if there is an in-game option for that.
Anyway, you could open the folder Roundscape Adorevia 5.8B\www\fonts
and replace the file Curse Casual.tff
(and maybe curse-casual.tff
too) with your favorite font.
I guess you have also to edit the file Roundscape Adorevia 5.8B\www\js\plugins.js
with Notepad++ where it says:
- (line 6) "Default Font":"Curse Casual","Font Size":"28"
- (line 11) "Curse Casual","Font Size":"28","Font Size Change":"12","Font Changed Max":"96","Font Changed Min":"12"
I mean, those numbers may not work with the new font.
Probably a monospaced (fixed-width) font would work better, but I never tried to replace the in-game font.