Thank you for contacting us.
RadMenu is designed to behave the same way like the standard windows menus. Therefore it rolls back its sub menus when the user clicks on some other control and not when mouse leaves the menu.
In fact, you are the first one who requests such a feature. We can consider adding this feature if more people request it.
In case, you have further questions, do not hesitate to write us.
the Telerik team