The Cowboys listed their two-time Pro Bowl quarterback as questionable for Sunday's game after he didn't participate in practice, the last one before playing at St. Louis.
Romo has a broken pinkie on his throwing hand, and a source told ESPN's Ed Werder that Romo continued to have trouble gripping the ball Friday.
Romo will dress for the game but it remains to be determined whether he or Brooks Bollinger will be the No. 2 quarterback with the other likely serving as the inactive third quarterback.
During the early portion of practice open to reporters, Romo mimicked throwing motions and lobbed only a couple of balls, but mostly stood and watched with his injured right hand hanging to his side or clasped behind his back.
Other than confirming Romo's status, coach Wade Phillips wouldn't elaborate when he made a brief appearance in the locker room after practice.
Cowboys owner Jerry Jones said on his weekly radio show Friday morning that Romo "looks like he'll be able to play Sunday." Jones said there was no chance that Romo could reinjure the pinkie because of the cast-like protection on his hand.
"It will be up to him. If he is feeling good and the pain is good, then it's likely he'll play," Jones said. "It's down to can he handle the pain?"
When Phillips was asked if he had been told Romo couldn't do further damage to the finger, the coach responded, "Dr. Jerry. Whatever Jerry says, I'm going with."
Jones said Romo was able to snap off some hard throws Thursday, and he talked about how important it was to win Sunday's game.
"We shouldn't compromise ourselves relative to our win-loss record," Jones said on 1310 The Ticket. "We got to get in the playoffs."
Romo's right hand was wrapped Friday, a fabric covering whatever protective device was being used to apparently stabilize the pinkie, with only the tips of three fingers exposed. His index finger and thumb were free.
Johnson, the 40-year-old backup in line to get his first start since 2006 for Minnesota, and Bollinger threw passes during early drills, while Romo lobbed a few passes but mostly stood and watched.
Romo was expected to miss up to a month (three games with an open date) after he broke his right pinkie when he was sacked on the first play of overtime in last weekend's 30-24 loss to the Arizona Cardinals. But Romo told coaches earlier this week he wanted to try to play.
Romo hasn't spoken in the locker room this week.
Before even taking a question Friday, Phillips made it clear the Cowboys were confident in Johnson, who has thrown only 11 passes -- all in the 2007 regular-season finale -- since arriving as Romo's backup last year.
"If Brad plays at quarterback, our team is ready to play with Brad. We have confidence in him, we feel like we can win with him," Phillips said. "Tony's really the bonus guy in this situation."
Information from The Associated Press and ESPN.com's Matt Mosley was used in this report.