Messi started the fixture on the bench after missing Friday's training session due to the birth of his second son, but the Argentine scored Barca's second in their 2-1 success.
Roberto, who is currently filling in at right-back for the Catalan club, has said that "there is nobody like" Messi, who has now hit 416 goals in 488 games for the Spanish giants.
"There is nobody like Leo. He's a father again, he could not train with us, but today he decided the game," Roberto told the club's official website.
"The team played very well the whole match and Leo was decisive when he came in. It's true we have two tough away games but now we only have one. We're thinking about Roma and the Champions League because it is always important to start off with a win."
Barcelona will travel to Roma in their opening Champions League group match on Wednesday.