The Broncos sit in fourth place after the first game of the final round, but will be overtaken by North Queensland if the Cowboys beat the Titans on Saturday.
Canterbury is also an outside chance of passing last year's runners-up, but would need to beat South Sydney by 45 points on Friday to make that happen.
Regardless of how it ends up, Brisbane will happily take the two points for a fifth-straight week although the performance left a bit to be desired with the playoffs looming.
The Broncos were coming off a win over the table-topping Storm but started as they have the vast majority of their games in the back half of the season, with questionable ball-handling and lacklustre defence, allowing the Roosters to jump out to a 12-0 lead.
First, they opted not to contest a Mitchell Pearce bomb, allowing former Bronco Dale Copley to jump over Matt Gillett and touch down in the seventh minute followed by a penalty goal to Blake Ferguson, after regular goal-kicker Latrell Mitchell succumbed to a hip injury.
More missed tackles and enterprising football from the second-last Roosters then saw Connor Watson cross in the 27th minute, but the next time the visitors attempted to pierce the line, the kick only found Corey Oates, who took off up-field.
A strong chase and ankle tap by rookie winger Joseph Manu stopped Oates from going the length of the field, but five-eighth Anthony Milford took advantage of the back-tracking defence to dive over in the 35th minute and suddenly it appeared the Broncos had flicked a switch.
The next set saw hooker Andrew McCullough reef a kick from beyond halfway towards Daniel Tupou's and when the Roosters winger arrived he made a meal of the clean-up, allowing Brisbane speed demon James Roberts to touch down.
Brisbane native Mitchell Frei then missed a shot at penalty goal after the siren, meaning the Roosters only led 14-12 at the break and the hosts were able to square the ledger with their own penalty goal from right in front shortly after the resumption.
The Broncos hit the lead in the 56th minute when a left-side shift fell apart and Darius Boyd flicked a pass back to Milford, who spun it long towards centrefield and from there it was a simple matter of putting the ball through the hands to find Jordan Kahu on the right wing.
Kahu nabbed a second after an excellent one-on-one strip by Ben Hunt saw Roberts fly down the right and kick back in-field, allowing the winger to dot down with five minutes left in the game.
But coach Wayne Bennett would not be 100 per cent confident ahead of the first week of the finals as Brisbane completed just 72 per cent of their sets, thanks mostly to 12 costly errors.
The defence, which conceded no points for the final 50 minutes, was also aided by slopping ball-handling from the Roosters.