Some Texans fans cheered on Sunday when Schaub left an eventual 38-13 loss to the visiting Rams with an ankle injury.
"It's truly, truly unfortunate," Roethlisberger said on 93.7 The Fan during his weekly radio show. "Booing when somebody gets hurt, it was just sickening. It's just so hard to understand, especially your home crowd."
The Pittsburgh Steelers quarterback also took issue with fans loitering near Schaub's Houston home following a 34-3 loss at San Francisco on Oct. 6. Schaub set an NFL record in San Francisco by throwing an interception that was returned for a touchdown for a fourth consecutive game.
Schaub, who is married and has three young daughters, was concerned enough about possible retaliation from fans who drove back and forth in front of his house and took pictures that he called Texans' security.
"When people were showing up at his house to do negative things, that's cause for some action from the player," Roethlisberger said. "That's your family. When we're on that field and we're in that stadium you can boo, you can yell at us but when we step outside we're human beings just like everybody else. We've got feelings, we've got family."
Coarse behavior directed at quarterbacks by their hometown fans is nothing new. Some Steelers fans threw trash in Tommy Maddox's yard in 2005 following a 23-17 overtime loss to the Jacksonville Jaguars.
Maddox threw three interceptions that game while playing for the injured Roethlisberger.
Roethlisberger and Schaub were in the 2004 NFL draft class together and have known each other for years.
The Steelers quarterback said the best thing Schaub can do is not let some fan behavior distract him as he tries to rebound from what has been a nightmarish season so far.
"I think in that situation you just have to approach it like, 'You know what, I'm going to play for my teammates, my brothers, my coaches' and on his mind he has to sit there and say it wasn't every fan," Roethlisberger said.
"He has to take the mindset that there's still a bunch of fans out there that are rooting for me, supporting me and that would be the mindset I would encourage him to go out there with."