The same rules apply to historical romance novels. Of course the settings differ and the plot revolves around the pageantry and romance and events of days gone by. One of the problems beginning writers often make is that they place too much emphasis on plot when they should be concentrating on developing strong characters. Remember that this is fantasy based on reality. The characters are usually larger than life and are the major element in a romance.
Emotion is an essential ingredient.
A critical situation. The critical situation is usually the event that triggers the conflict. Obstacles we put in the way of the character's progress toward goals, both internal and external, temporary and long term. The characters' pursuit of goals, either mutual or opposing goals, is one of the strongest sources of conflict. It is conflict that provides drama.