I've set the OptionsButton Visibility to Collapsed
ribbonBar.RibbonBarElement.OptionsButton.Visibility = ElementVisibility.Collapsed;
and indeed I don't see the small button appearing in the footer of the StartMenu but for some reason I see a default RadMenuItem appearing on the left column of the StartMenu with the text "Options <application name>".
I have also tried (with no luck)
ribbonBar.OptionsButton.Visibility = ElementVisibility.Collapsed;