Roethlisberger was in serious but stable condition, Dr. Larry Jones, chief of trauma at Mercy Hospital said before surgery.
The player's agent, Leigh Steinberg, described the injuries to The Associated Press and said he did not know if there was further damage.
"He was talking to me before he left for the operating room," Jones said. "He's coherent. He's making sense. He knows what happened. He knows where he is. From that standpoint, he's very stable."
Roethlisberger's mother, Brenda, was crying as she arrived at the hospital.
Steelers president Art Rooney II said the team was "encouraged by the early reports from the medical team" at the hospital. "I am sure Ben knows that we are praying for his complete recovery."
The 24-year-old Roethlisberger was without a helmet, police said. He has said he likes to ride without one, a habit that once prompted a lecture from Pittsburgh coach Bill Cowher.
CBS News correspondent Bob Orr reports Steelers Hall-of-Fame quarterback Terry Bradshaw also lectured Roethlisberger.
"Do you not care about your organization, your teammates and your fans?" Bradshaw asked in 2005. "Those things are dangerous."
Roethlisberger was on his black 2005 Suzuki Hayabusa — the company calls it the world's fastest bike for legal street riding — and heading toward an intersection on the edge of downtown. A silver Chrysler New Yorker traveling in the opposite direction took a left turn and collided with the motorcycle, and Roethlisberger was thrown, police said.
The other car was driven by a 62-year-old woman, police said. They didn't immediately release her name and no charges were filed.
Witness Sandra Ford was waiting at a bus stop when she said she saw the motorcycle approach. Seconds later, she said she heard a crash, saw the motorcyclist in the air and ran toward the crash scene.
"He wasn't moving and I was afraid that he had died. ... He wasn't really speaking. He seemed dazed but he was resisting the effort to make him stay down," said Ford, who didn't realize the motorcyclist was Roethlisberger.
Police spokesman Lt. Kevin Kraus said police and homicide units were leading the investigation, a standard practice when there is an accident with critical injuries.
In only his second year in the NFL, Roethlisberger helped guide the Steelers to the Super Bowl title in February at age 23. Training camp for next season begins at the end of July.
Several teammates, including backup quarterback Charlie Batch, linebacker Joey Porter and safety Mike Logan, arrived at the emergency room.
Some fans also gathered at the hospital, including Juanita Clark, who sells Steelers paraphernalia.
"I just feel like he's a family member," said her daughter, Loretta Clark.
Roethlisberger has said in the past that he prefers not to wear a helmet when riding his motorcycle. He has pointed out Pennsylvania's state law requiring helmets to be worn was repealed in September 2003.
In May 2005, Cowher warned him about safe riding after Cleveland tight end Kellen Winslow Jr. was injured in a motorcycle accident. Winslow tore knee ligaments and was lost for the season.
"He talked about being a risk-taker and I'm not really a risk-taker. I'm pretty conservative and laid back, but the big thing is to just be careful," Roethlisberger said at the time. "I'll just continue to be careful. I told him we don't ever ride alone, we always ride in a group of people, and I think it makes it even more safe."
Roethlisberger continued to ride after Winslow's accident and that angered Terry Bradshaw, who quarterbacked the Steelers to four Super Bowl victories during the 1970s.
Visiting the Steelers' training camp last summer, Bradshaw remarked: "Ride it when you retire."