So basically, work after residency includes academic positions or private practice. I know some people in academics, some in private practice. Now, there are radiology reading firms that work with clients (dentists, oral surgeons, ENTs in some cases) and hire the radiologists as employees or independent contractors and provide them with the cases and pay per report. Now, some do extremely well, some decent enough.
The other option is too find clients on your own, some of the radiologists conduct CE courses, become a part of study groups and so forth to introduce themselves to other dentists/specialists.
The business aspect includes opening a diagnostic imaging center of your own, which is more common in Asian countries then here as a lot of the dental offices buy their own machines unlike a lot of other places, especially the developing countries.
As far as financial output is concerned, it varies a lot between one radiologist and another but a person is doing very well and gets a lot of cases to read, can make pretty good money, somewhat comparable to other dental specialists (not as much as surgeon though obviously).