[Powertrain]

Yeah, I was trying to avoid using flyout menu as I already have the dropdown styles just with css, no JQuery but need the code to display root categories as main links and on hover to display that category subcategories in a list.

In your case you could create new tpl file (e.g. topmenu.tpl) copy flyout code to it and call it in your home or header file (depending where you want it to show). Of course you'll have to remove {if flyout enabled...} code so you can keep module disabled for sidebar menu. You might need to clone categories.tpl too for use on your new topmenu, not sure without looking at the files.
Something along those lines.