In many ways, San Francisco’s varied approach to offensive football mirrors the background of Roman, its offensive coordinator. He started coaching with the Carolina Panthers in 1995, as a strength and conditioning assistant and defensive quality control coach, the lowest rung on the N.F.L. coaching ladder. He would later instruct tight ends, quarterbacks, offensive linemen and running backs, in Houston and Baltimore and at Stanford University.

He joined the Cardinal in 2009 and helped oversee an offense that was among the most productive in the college game. He helped develop Andrew Luck and then joined Harbaugh in San Francisco, where he helped Smith revive his career and helped turn Kaepernick into a household name.

Roman’s offense, like his background, cannot be quantified by a single position or philosophy. He views the rushing game as the basis for all offense, but sometimes this season he leaned toward the pass and sometimes, like last week against the Packers, he asked the quarterback to run wild. He called plays as if averse to patterns, which drew criticism when the offense stalled.

“Every game is different,” Roman said this week. “No matter how you look at it, you have to pay homage to the football gods every week in practice, in meetings, in your preparation. Then you have to go out and perform on game day.”

Spoken like a true coach. This week, Roman’s attitude typified that of the 49ers, a loose bunch that spoke of a different locker room vibe compared with that for the N.F.C. championship appearance last season, which San Francisco lost. Moss, the moody veteran receiver whom Harbaugh said Friday that he wanted to bring back next season, sauntered toward his locker, laughing, smiling, joking with his teammates.

Offensive lineman Joe Staley, the anchor of a unit considered among the best in the N.F.L., sat surrounded by reporters. “We don’t have to go outside ourselves and do anything crazy in this offense,” he said. “We’re ready to go with whatever we put out there. We know what to expect this season.”

The 49ers know what a conference championship game feels like, but the Falcons must prepare for Roman’s whims. When Roman met with the news media this week, he talked about Gore’s adjustment to the read option, about James’s versatility, about Kaepernick’s ability to block out distractions — all those moving parts at his disposal.

“I don’t think there’s any hump we feel we have to get over,” Roman said. “It’s a must-win game. It’s win or go home. Everybody has a real true sense of that.”