Where to Find and Catch Rockruff
From Pokemon Go Wiki
Rockruff are found and captured in Nest and Habitat locations.
Nests
Rockruff Nests are locations that consistently spawn Rockruff.
Habitats
Rockruff Habitats are spawn locations where Rockruff is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: