RootObject.cs

    [MarkupExtensionReturnType(typeof(ContentControl))]
    public class RootObject : MarkupExtension
    {
        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            var rootObjectProvider = (IRootObjectProvider)serviceProvider.GetService(typeof(IRootObjectProvider));
            return rootObjectProvider?.RootObject;
        }
    }

window.xaml

    <ContextMenu DataContext="{Binding DataContext, Source={_3RdParty:RootObject}}">
        <MenuItem Header="Remove" Command="{Binding CmdRemoveControllerOperation}" CommandParameter="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}" />
    </ContextMenu>