Using jQueryRotate to apply non-90degree rotation should not cause any issues, however, modifications applied with it will not be stored to the image when saved. To do so, a custom logic should be implemented on the server.
At present, RadImageEditor does not offer the ability to implement custom commands that require server-side implementation. We do have planned to provide the ability to apply server-side custom manipulations for one of the next versions of RadImageEditor, but for now it is not possible to apply non-90 degree rotation.
the Telerik team