There are three types of Romantic Fiction:
The Novella: these books are short stories and are about 25,000 words.
Category: these books are also considered short stories and fit into a publisher's clearly delineated grouping and are usually about 55,000 words.
Single-Title: these books are longer and cover a large range of subject matter. A single-title romance has more of everything — more plot, more characters, and more romance. They are usually around 100,000 words.
Historical (genres in this category: Highlander, Regency, Victorian, Western, etc.)
As you can see, there are many sub genres in romance and many romance novelists combine genres to widen the salability of their books in the marketplace. Crossing genres adds extra elements to make the novel more interesting to the reader.
I just finished reading a Contemporary, Time Travel, Paranormal. My book Desirea’s Escape is a Regency, Time Travel, Historical Romance, with paranormal elements. The key to marketing is to make sure your novel is tagged correctly so that readers will know what they are buying.