I can't change language. In the main page is written that inside game, but in game and inside I do not see such an option.
I haven't got the GOG version installed, but I believe if you look in the games install directory .../DragonAge/bin_ship
And run DAOriginsConfig.exe
On the video tab you will see Language & VO Language.
On my EA Origins version I only have the English option, but I think I read somewhere that the GOG version installs all available languages.
If they do, that is where to change it.
Then click on Dragon Age: Origins at the top, and save settings.
See the attached pic: