I waited about 10 days between 4th and 5th session and had 4 Failures to eject in 28 shots (4 -7 round gun fulls) In each case the brass did not eject and was lodged in the gun as the next round tried to feed and got stuck because the brass was in the way. I used Winchecter WB during this session same lot as in prior sessions. About 50 of past 165 rounds were Winchesters without problems. I would appreciate any advice about what I have done wrong. Was it I waited 10 days since last cleaning carried the gun and did not fire. Can the R9 go that long between cleaning even if not fired? I did not see lint or dust on gun before firing in 5th session. What generally caused failure of brass to eject out of the gun? 
Waiting 10 days between cleaning sessions is really no reason for a pistol not to function.
There are a number of reasons for a pistol not to eject.
Probably the number one cause in small pistols like this is a form of limp-wristing. That is, allowing the pistol to move around (particularly ride up) too much during recoil. That takes some of the momentum away from the slide so that it doesn't get back to the ejector firmly enough to kick the old brass out.
Usually, limp-wristing will result in a stovepipe jam in which the spent brass is sticking out the ejection port, but didn't have enough energy to get out of the way of the next loaded round trying to get in the chamber.
My suspicion would be that maybe you got comfortable with your new pistol and relaxed too much when shooting it this last time. If you got stovepipe type jams, I'd suggest that you try another range session making a conscious attempt to hold it very firmly.
Sometimes extractors will have a soft spring and not clear the brass from the chamber. Again,
usually that's seen as the brass left in the chamber with next round jammed up against the spent primer of the fired round.
I emphasized usually above because those indicators aren't cut in stone. Infrequently, you can also get an ejector issue that will mimic either one. However, the ejector on the Rohrbaugh is pretty robust and would be my last suspicion.