There is a list of all Nora Roberts books online. It can be found as "Nora Roberts bibliography" on Wikipedia.org. This specific list contains the titles of all her novels and novellas that were published up to beginning of September, 2015.
Nora Roberts writes books under her actual name and also using pseudonyms such as Jill March and J.D. Robb. The Wikipedia bibliography lists all the books that were published using her actual name and pseudonyms according to the book title and year of publishing for easy reference.
Another list containing the titles of all her books that were published using her real name and pseudonyms can be found on Noraroberts.com. This list can be downloaded in PDF format for printing or viewing on the computer.