There are many, many Internet sites about the Roswell Incident. Most were written by interested individuals, but a few include links to primary source material:
When you know the title of the item you are seeking, the first step is to search by title in an online catalog.
In all of these catalogs, you can use the subject headings:
Unidentified flying objects -- Sightings and encounters -- New Mexico -- Roswell
Roswell Incident, Roswell, N.M., 1947