Roberto, who started off as a midfielder and then moved to right-back, told Movistar that "we knew the start of the season is complicated and to start with a win is very important," after Barcelona beat Alaves 3-0 at Camp Nou.
"We expected Alaves would be difficult because they tighten up at the back and it was like that in the first half, but in the second we found more space and the goals arrived," said Roberto.
On his change of position, Roberto said: "In pre-season I played more as a pivote and after in the Super Cup as a full-back, but I'm happy helping the team in whatever position."
On two-goal Messi, he added: "In these type of games you always expect Leo to do something and he did it. He got the 6,000th goal and he had already got the 6,000th and it's hard for him to get the 7,000th - but we are delighted to be here with him."