The deputy coach will take temporary charge of the Liga side following the announcement that Tito Vilanova must take time out to receive treatment for cancer
Roura, who came through the club's La Masia system as a player, will take over the day-to-day running of the side while Vilanova undergoes treatment.
Barca's chief Andoni Zubizarreta told a press conference: "Roura will sit on the bench at Valladolid [whom Barca face on Saturday in La Liga], but the coach is Tito.
"Tito isn't here now, Jordi is here, and all the training staff are here to help the players to work at their maximum."
Roura began his career as a player at Camp Nou, and then became a coach in Japan with Yokohama Flugels before moving on to Terrassa FC until 2007.
The 45-year-old then moved on to CE L'Hospitalet in the Spanish third tier, before he joined Pep Guardiola's technical staff in 2009, charged with analysing opposition sides.
Following Guardiola's departure in June - and Vilanova's promotion to coach - Roura became Barca's assistant manager.
Vilanova, who had surgery on a cancerous tumour on a gland in his throat in November 2011, is set to undergo treatment on Thursday.
He is expected to remain in hospital for three or four days, and then faces chemotherapy and radiotherapy sessions over the following six weeks.
"Tito had scheduled a routine test for yesterday. At noon we thought everything was OK," continued Zubizaretta.
"At 7pm we were informed there could be a problem and this morning we got the exact diagnosis. Tito sent us a calming message - he knows it's a complicated, tough situation, but he has experienced it before and we are all going to see it overcome again.
Barcelona president Sandro Rosell added: "Our trust in him is total, the club is united and strong and we are capable of overcoming anything."
Meanwhile defender Eric Abidal returned to training with the first team following a nine-month absence after liver surgery.
The France international has not played competitive football since February 26, but hopes to return to La Liga action within weeks.