I do both.
I have an 85 gauge rocker which does a good job. 65 gauge produces a slightly more robust burr. Be prepared to spend a LONG time rocking though. it is a very labour intensive process. Here in the UK there is a supplier (Martin Maywood)of excellent pre rocked plates not done by machine. I have used these and they are first class. He supplies whatever gauge you want.
I also strongly recommend getting your hands on a copy of 'The Mezzotint, History and Technique' by Carol Wax. It is out of print but can be found at a half decent price with a bit of Googling. If you do plan to rock your own plates she gives clear instructions and describes the various rocking patterns needed to get an evenly rocked plate. A rocking pole or jig and weights make the task easier too. Julie Niskanen supplies a simple jig but if you are handy it is not difficult to make your own rocking pole.