We know that Ross is in Black Widow, and we know that Widow is a prequel, taking place shortly after the events of Captain America: Civil War.
Ross seems like someone who would be able to convince Sharon Carter (Emily VanCamp) to work for him.
Ross also seems like the kind of person who’d want John Walker at his disposal, given his fascination with the super soldier serum.
If Julia Louis-Dreyfus’ character has been on the scene since that point, then it’s very possible that she was working for Ross, and that Ross might also be The Power Broker, a behind-the-scenes manipulator in The Falcon and the Winter Soldier.