Roczen, who arrived with the red plate and the series lead, won his heat race and made a good start in the main event, circulating inside the top three.
After making a pass for second, Roczen came up short on a triple, landing on the face of the jump and went down hard.
It took him out of any contention for the race win, but he steadily got to his feet after recovering his breath, remounted, and came through to finish 15th.
Roczen, who now sits second in the championship, four points off the series lead, said, “My heat race was really good and I got off to a great start in the main event, battling with Chad Reed and Andrew Short.
“I made the pass on Reed and I tried to triple and came up short. I hit my face and my goggles on my handlebars so I had to stop and just check myself for a minute.
“Luckily I got back up and kept going. Those are important points.”
The AMA Supercross series returns to Anaheim next weekend for the series’ third and final visit of the season to the Angel Stadium for round five.