#1 Ask romance authors. If you appreciate the delivery, characterizations, and plots of their romance novels, then ask romance authors for recommendations. They can give you firsthand opinions on an editor’s services and pricing. Read the editor’s website prior to contacting. All editors should have a site, just like authors. (Though not all great editors do, just like authors.)
#2 The Editorial Freelancers Association (EFA) is a professional organization for editors, much like the Romance Writers of America is for authors. Except (to my knowledge) not many romance editors are members, and the EFA is not romance-genre specific. However, authors can still search the EFA’s database for free.
#3 Look in the front of self published romance novels (see novel appreciation criteria listed in #1). Editors’ names should be near the copyright. If not, sometimes they’re mentioned in the acknowledgments. Search those editors and start reading. If they have social media, see who they interact with. It’s likely they talk to other editors and their social media reflects their personality. If you don’t like your editor, it may be hard to work with him or her.
#4 Publishing houses often list their editors on their websites and those editors often freelance. Only consider publishing houses that publish books you appreciate (see novel appreciation criteria listed in #1). These editors cannot guarantee a book deal even if you pay them to edit your manuscript. Let them know prior to working with them if you intend to submit your manuscript to their publishing house. Again, search their websites and social media.
#5 Search “romance novel editor.” I assume that’s how you got here. There’s nothing wrong with finding your editor through Internet research, but your research should not stop with a Google hit. Read the editor’s website and track his or her social media. Look for references and contact those references. Ask for a sample edit to ensure your working relationship will be a productive one.
#6 Go to Twitter, search for big-name romance-genre editors, and scroll through their followers. (Editors like Sue Grimshaw, Angela James, and Liz Pelletier.) Some of their followers will be freelance editors.
#7 Go to Twitter, search for big-name romance-genre editors, and see what Lists they belong and subscribe to. Some of these Lists are titled Editors and some of the members are freelance. Also search through romance authors, bloggers, and reviewers’ Lists on Twitter to see who keeps a List of editors. (Like this one and this one, though all editors listed may not be romance editors.)