After the Rockliffe series, had then jumped into The Shadow Earl, which in the latter part of that story introduced a number of interesting old family names and reconnects with others from Rockliffe. One realizes, there is much to these names that come up, and if read after the Roundheads & Cavaliers as the civil war explodes, it would have connected. However, even this way it has been very interesting following different characters knowing some will emerge, or their generational families would in later books.
As for the Roundheads & Cavaliers, the author Riley did a lot of deep research to tell these stories, stories that had characters in so many different religious and political polarities that became central to the civil war. Horrible hard times, and Stella does not pull any punches in the writing of them.
Lastly, if I had read Stella's books (have not finished) before any of the other Romance novels, none would have been forgotten. With these books being read now, they do indeed set the stage for the years that followed.