Defending Dakar motorcycling champion Coma regained the overall lead in his thrilling duel with France's three-time winner Cyril Despres with Monday's stage win.
Roma claimed his second stage of the race in his Mini though French Dakar legend Stephane Peterhansel retained the overall lead.
Coma had been over seven minutes behind Despres going into the 477km stage from Copiapo but the Spaniard benefited from his fellow KTM rider having problems early on when he got stuck in a boggy patch which had not been highlighted in the racebook.
Despres eventually came in 17min 20sec in arrears of Coma but race stewards took into account his time spent in the bog and amended his time accordingly to 9min 14sec – he trails Coma by 1min 26sec in the overall standings.
Coma's fourth stage win – his 20th overall – of the Rally was in a time of 5hr 03min and 52sec, seven minutes faster than his team-mate Portuguese rider Ruben Faria while the latter's compatriot, Yamaha rider Helder Rodrigues, was 7min 10sec adrift in third.
"It is not winning specials that counts, but winning the race," Coma said.
"And I know there is still a long week of racing ahead."
Roma – a former winner in the motorbike section – finished in a time of 4hr 25min 44sec, five seconds quicker than American Robby Gordon, driving a Hummer, while former overall leader and fellow Mini pilot Krzysztof Holowczyc was third 2min 04sec adrift.
Peterhansel – a six-time Dakar motorcycling champion and three-time car winner – came in fourth 5min 38sec slower while defending champion Nasser Al-Attiyah of Qatar was fifth in his Hummer but lost more time on the overall leader as he was 8min 09sec adrift.
Gordon slashed three minutes off 46-year-old Peterhansel's overall lead and trails him by 7min 36sec.