There are several places. Open Library is a great resource. It has a vast collection of books in digital form, and you can search specifically for romance novels and download them for free as ebooks. Additionally, Google Books also has a selection of free romance novel ebooks. Some are fully available for free, while others may have previews that can still give you a good taste of the story.
One place to find free romance novel ebooks is Smashwords. It has a large number of self - published and independent works, many of which are free. You can search by genre to find the romance novels you like. Another source could be the author's own website. Some authors offer their romance novels as free ebooks directly on their sites as a way to gain readership and promote their work.
You can try Project Gutenberg. It offers a wide range of classic literature, including some romance novels, all for free in ebook format. Another option is ManyBooks, which has a large collection of free ebooks, and you can easily find romance novels among them. Also, some libraries now provide digital lending services for free ebooks, so check with your local library.