The Malian earned the hosts a precious point after Carlos Tevez looked to have sealed the Scudetto with his stunning free-kick, just seconds after Vasilis Torosidi's dismissal
Carlos Tevez looked to have extended the Bianconeri's advantage over Rudi Garcia's team at the top of the table to 12 points when he curled home a delightful 25-yard free-kick shortly after the hour mark at Stadio Olimpico.
Roma's task was made even tougher by the fact Vasilis Torosidis had been given a second yellow card for the foul on Arturo Vidal that led to Tevez's free-kick.
However, Keita's close-range header found its way in 12 minutes from time to earn the hosts a 1-1 draw in a fiery, disjointed encounter littered with bookings and fouls and devoid of much goalmouth action.
Neither Gianluigi Buffon nor Morgan De Sanctis were really tested in the first half, and it was only after Torosidis received his second caution - the seventh of the game - for a trip on Vidal that the game burst to life.
Tevez then superbly curled home his 15th league goal of the season, only for Keita to snatch a point for Garcia's men.
Juve boss Massimiliano Allegri will likely see the draw as a job well done, though, as Roma missed the chance to close the gap to six points with 13 matches remaining.
Roma enforcer Daniele De Rossi set the tone for a scrappy encounter when he scythed down Vidal just 17 seconds in.
Neither an unfit Paul Pogba nor the injured Andrea Pirlo were beside Vidal in Juve's midfield, but Allegri's team edged the opening stages regardless.
Chances were few and far between in the opening 20 minutes, as Kostas Manolas was forced to clear Vidal's dangerous pass with Alvaro Morata lurking behind him before Roberto Pereyra failed to connect with Patrice Evra's delivery from the left.
Tevez burst forward and shot wide three minutes before the break, but the sides went in level after a low-key half in which neither side registered a shot on target.
Pereyra fired across De Sanctis early in the second period as Juve continued to have the better of the play, despite Roma's greater need for all three points.
However, any hopes Roma had of closing the gap with a victory were dashed just after the hour, as Torosidis received his second yellow card and Tevez compounded their misery with his wonderful free-kick.
But Roma kept battling, and were rewarded Keita nodded Alessandro Florenzi's set-piece back across goal and Marchisio unable to stop the ball creeping over the line as the home side just about stayed in the title race.