Coach Mike Tomlin said Tuesday that the X-ray for Roethlisberger's rib injury was "not clearly readable" during the halftime evaluation, possibly due to dated equipment.
Further tests in Pittsburgh showed multiple rib contusions, though Roethlisberger is expected to play Sunday against the New England Patriots.
This is the latest news in a busy time for the reeling Steelers, who are also trying out kickers in light of Chris Boswell's struggles.
"We never really had a full understanding specifically what the injury was on the stadium site," said Tomlin, whose Steelers have lost three straight. "Because of the lack of information, we thought the best thing to do, the most prudent thing to do, was to only to make Ben available in emergency-like situations."
Roethlisberger exited the game with 10 seconds left in the second quarter and spent most of the second half on the sideline, returning with 5:20 left to orchestrate a touchdown drive. The Raiders countered with a fourth-down score at the goal line, and Boswell slipped on a 40-yard field goal attempt that would have tied the game.
"The team -- and when I say 'the team,' it's [general manager Kevin] Colbert, it's everybody -- was kind of like, 'Let's let this thing play out,' because I think it was still the unknown of the injury," Roethlisberger said during his weekly radio show with 93.7 The Fan. "I think what they were probably worried about was making it worse because we didn't know what the injury was. You want to play unless you think you're going to hurt your team."
Roethlisberger said he told Tomlin he was available if needed.
As for Boswell, his six missed field goals and five missed extra points have forced the Steelers to look elsewhere, but it sounds like Boswell might get another chance this week.
Boswell is 4-for-8 in Pittsburgh's five losses, but after signing a contract extension in August worth around $20 million, the Steelers would absorb $4.8 million in dead money in 2019 should they cut him.
"We acknowledge that Chris has struggled to find consistent footing," Tomlin said. "We're willing to explore options to give us the very best chances of that ball going through the uprights this weekend. That said, those options include Chris."
"He had a really impressive week [of rehab] last week. We'll see what this week holds," Tomlin said.