Roura is deputising for Tito Vilanova, who was discharged from hospital on Saturday after undergoing an operation on his parotid gland on Thursday, and saw his side take a 1-0 interval lead when Xavi Hernandez tapped in Jordi Alba's cross.
The Spain midfielder then set up Lionel Messi for his 91st and last goal of an extraordinary 2012 and, after Javi Guerra pulled one back, Cristian Tello rounded off the win in injury time.
Real Madrid's fading title hopes were hit with another blow after slumping to a 3-2 defeat at Malaga to fall 16 points behind Barcelona.
Roque Santa Cruz struck twice in three second-half minutes to help fourth-placed Malaga heap the pressure on Madrid coach Jose Mourinho, who omitted captain Iker Casillas from his starting line-up.
Isco put Malaga ahead in the 48th minute before an own goal from Sergio Sanchez drew Madrid level midway through the second half.
But substitute Santa Cruz, who had been on the pitch less than 10 minutes, stunned the visitors by putting Malaga 3-1 ahead with a double strike in the 73rd and 76th minutes.
Benzema pulled another goal back with eight minutes remaining but Madrid could not find an equaliser.
Apono and Helder Postiga were on target as Real Zaragoza ran out impressive 2-0 winners at Athletic Bilbao.
Zaragoza had won just one of their last five coming in to Saturday's game but looked in fine form as they eased to the three points courtesy of Apono's penalty and Postiga's effort shortly before the interval.
Real Mallorca got their first win in 15 games in all competitions as they came from behind to beat Champions League-chasing Real Betis 2-1 at the Benito Villamarin.
Benat's free-kick had given the hosts an early lead, but Victor brought the Islanders level with a fine header on the half-hour mark.
And the comeback was completed just two minutes into the second half when Mario's challenge on Victor was deemed to have taken place inside the area and Javi Marquez comfortably slotted home the resultant penalty.
Granada secured only their second win in seven league games with a deserved 2-1 victory over Osasuna.
Nino had fired the hosts into an early lead with a looping header from Raoul Loe's flick-on, but Granada dominated thereafter and should have been level well before Diego Mainz did find the back of the net from Dani Benitez's free-kick four minutes before half-time.
Benitez himself then put his side ahead two minutes into the second period with a wonderful left-footed strike.
Atletico Madrid bounced back from their Nou Camp thumping with a hard-fought 1-0 win at home to struggling Celta Vigo.
The capital club, beaten 4-1 in Barcelona last time out, closed the gap on the La Liga leaders to six points thanks to substitute Adrian's 77th-minute goal.
The forward broke the deadlock just five minutes after his introduction, but the hosts had to hold on for the victory after Joao Miranda was sent off four minutes from time.
Earlier on Friday, Ernesto Valverde got his first home win since taking charge of Valencia as Los Che saw off Getafe 4-2 at the Mestalla.
The hosts were 2-0 up inside seven minutes as Roberto Soldado headed in from Sofiane Feghouli's cross before the Valencia captain turned provider to set up Jonas to curl past Miguel Angel Moya.
Getafe soon had a foothold in the game as Alvaro Vasquez turned in Xavi Torres' pass from a narrow angle, but Valencia restored their two-goal advantage on the half hour as Ricardo Costa powered home a header from Tino Costa's corner.
Alexis reduced the deficit once more on the hour mark with another fine header, this time from Abdelaziz Barrada's corner, but Valencia finally sealed the three points when Nelson Valdez swept home Jonathan Viera's cutback in stoppage time.
Real Sociedad defender Alberto de la Bella's second-half goal ensured 10-man Sevilla's recent dire form continued as the hosts won 2-1 at the Anoeta.
De la Bella netted in the 69th minute as the hosts extended their unbeaten record to eight matches in all competitions, while Sevilla have now collected just one point from their last five league matches.
The visitors did get back on level terms as Gary Medel cancelled out Carlos Vela's early strike, but De la Bella ensured they went home empty handed and their misery was further compounded when Andujar Coke picked up two yellow cards in the space of four second-half minutes.
Second-half goals by Nacho Martinez, Piti and Franco Vazquez guided Rayo Vallecano to a 3-0 victory over Levante as they ended 2012 with two consecutive victories.
Martinez opened the scoring just before the hour and Piti struck 10 minutes from time, both goals coming from fine strikes, before Vazquez pounced.
Victory guided Rayo to two points behind Levante who had been in a strong vein of form coming into the game with six wins and two draws from their past 10 La Liga matches.
Espanyol moved out of the drop zone following a hard-earned 2-0 victory over rock-bottom Deportivo La Coruna.
Former Portugal international Simao Sabrosa headed home just after the half hour in a match where the losers would have the unwanted position of going into the two-week winter break at the foot of the table.
In the closing stages, substitute Christian Stuani sealed the three points which moved Javier Aguirre's men into 16th place although they could find themselves back in the bottom three by Saturday.
Saturday's La Liga Results
Friday's La Liga Results
Thursday's La Liga Results