A basic brown gravy starts with a roue, to which is added pan dripping and/or beef stock. Then, depending upon what kind of beef gravy one is making, other ingredients are added. :-)
For instance, mushroom gravy doesn't usually contain any onions, OF ANY KIND, in it.
Onion gravy contains NO mushrooms and NO shallots; but does contain "sweet" onions finely chopped and sometimes parsley!
Both can contain wine, or not any at all.
The variations are many.
I know all that. I thought I already responded to this but it’s not showing up.
I’m just leading you on because I’m enjoying sparring with you.
And it’s spelled “roux” and not roue. You mix fat with flour (or other thickener) to help prevent lumpy gravy.
En Français, mademoiselle.