"Ben had a rib injury," Tomlin told reporters. "He was able to come back into the game. Nothing else to specifically mention."
The Steelers' signal-caller also wasn't in a mood to offer additional information during his press conference.
"I have what Coach said, a rib injury," Roethlisberger told reporters. "So we'll let him address."
The Steelers designated Roethlisberger as questionable to return after he stayed in the locker room after halftime for evaluation.
It is unclear exactly when the injury occurred, but within moments of the announcement, the FOX Sports broadcast showed numerous replays of Raiders defensive tackle Clinton McDonald sacking Roethlisberger at the 5:15 mark of the second quarter. Roethlisberger would remain in the game, however, and closed out the first half with a 1-yard touchdown pass to wide receiver JuJu Smith-Schuster.
With Roethlisberger in the locker room to open the third quarter, Josh Dobbs took the field and played through the period and into the fourth quarter. He eventually gave way to Roethlisberger, who returned to the sideline early in the third quarter, after the Raiders took a 17-14 lead with 5:25 left in the game.
"He got looked at at halftime," Tomlin said of Roethlisberger. "He got treatment. He came back out. We were waiting to see if he was going to be able to come back in -- he was. Probably could have come in a series or so sooner. But we were in the rhythm and flow of the game. He was ready to go when he got back out there."
The final two minutes of the game produced a back-and-forth affair between the two teams. Oakland scored a touchdown with 25 seconds left in the game for a 24-21 lead, but the Steelers got within range to attempt a field goal and a chance to send the game to overtime. Kicker Chris Boswell slipped, though, and his kick was blocked.
Roethlisberger finished the game completing 25 of 29 passes for 282 yards and two touchdowns. After re-entering the game, he completed 7 of 7 passes for 118 yards and a touchdown and a perfect 158.3 passer rating.
As for how he felt on the drive, all reporters received was a simple response from Big Ben: "OK."