Thank you for writing. Please excuse me for the misunderstanding. This can be done by adding a style sheet relation to your toggle button theme xml file. After you create your theme, open the xml in VisualStudio and collapse the BuilderData tag. Then you should see a <StyleRelations> tag and some relations inside. Replace the last relation with this one:
|<RadStylesheetRelation ControlType="Telerik.WinControls.UI.RadRibbonBar" ElementType="Telerik.WinControls.UI.RadToggleButtonElement" />
There is one more thing that needs to be done. While you are still in the xml file, change the theme name (second line in the file) to the theme you have currently set to the ribbon. For example, if your ribbon is using the "ControlDefault" theme you have to change the theme name of your toggle button theme to "Control Default".
After you do this, load your theme and tell me if this worked. I am looking forward to your reply.
the Telerik team