Roku is currently not supported in Turkey for full capability. Sorry, this is not what you want to hear, but I guess you bought abroad and self imported or had some non-Turkish website ship to you.
Roku device will work, but not all channels will be available.
The device (and account website) will show you the "rest of world" version of channel store. Which does not include Disney+, as you have found.
It will be decision of Disney (and other major channels) whether to list their channel in the "rest of world" channel store (probably not, Disney+ is not global). Not a Roku decision, Roku is just a platform for content providers to use.
Netflix is one of the few major streamers who does list in "rest of world". Unsure if Roku channel does.
There is no master reference list easily accessible to show which channels are available in which country, so I can't easily check.
Many smaller channels enable all countries by default (although sometimes won't serve content after install.
List of supported countries (also in main Roku Terms on support website, one EULA doc per supported country).
Please be advised that Turkiye is not an official supported region for Roku that is why you are unable to add Prime Video and/or Disney Plus.
Any Roku Player or TV can be activated to any Roku account, however, channel availability/access will vary from region to region. Channels that are currently available in any given region are certified for the Roku devices sold in that region.