(written from a Production point of view)
Rolando "J.R." Quinonez is an artist and actor who was the regular stand-in, body double, and photo double for Robert Picardo on Star Trek: Voyager and for John Billingsley on Star Trek: Enterprise. His only credited appearance was in the episode "Renaissance Man" as The Doctor disguised as a Hierarchy Alien where he was credited as Overlooker/The Doctor. Quinonez also played the original, non speaking version of Ferengi pilot Kol in the Star Trek: The Next Generation episode "The Price".
Picardo spoke in an interview about his work with Quinonez in "Life Line" during shooting for the special effects sequence, where he was Picardo's on-screen photo double. Quinonez played also a role in a Star Trek: Enterprise episode where he wore the costume from Tom Morga as Minnis in "Alliances". This information is from the costumer's tag and the costume was sold off on It's A Wrap! sale and auction on eBay. Other costumes which were sold off on the It's A Wrap! auction were Quinonez' photo double costumes from the episode "Virtuoso"  and another episode. 
Quinonez' other credits are as a casting associate in Blind Side (1993, with Jonathan Banks, Jorge Cervera, Jr., Josh Cruze, and stunts by Jimmy Ortega), as a production assistant in World Inside Me (1998, written, directed, produced and starring Star Trek visual effects coordinator/supervisor David Takemura), as a production assistant in the television series Dear John (1988-1992), and as a production staff member in the pilot episode of the television series Committed (2005).
In the position of a stand-in he has also worked on the television series Just Legal (2005-2006, guest starring Patti Yasutake, Julie Warner, Raphael Sbarge, and stunt coordinated by Vince Deadrick, Jr.), Teachers (2006, starring Matt Winston), and the pilot episode of Dirt (2007, starring Jeffrey Nordling and Mariette Hartley).