It depends on what you mean by rolling out of the barrel. If the balls are just leaving at a much lower velocity, check your tank and make sure it’s full. If not, try getting a smaller bore barrel. The stock Etha barrel bores out at a huge .693, which is large for regular paintballs. Reballs tend to be much smaller, so they don’t fit as well into the stock barrels. Try something with a .685 or even a .683 bore and it should fix the problem.
Another thing you could try is turning the velocity up. The lack of pressure combined with the small barrel bore can cause huge drops in muzzle velocity.
If you mean that when you point the gun down, balls are literally rolling out of the barrel, it’s an issue with your detents. Take off the eye covers (look here if you need help with that), then inspect the rubber detent on each side. Replace them if you see any damage.