I'm asking the United fans here. Did Ferguson used Rooney on the right wing? And did he play good on that position? If yes, he would have the ability to change Barca's system during the game. He and Messi could always swap positions to confuse the defenders. And if needed, he could be used in the midfield (only if needed). He is one of a few strikers who can be used on different positions. He is not a player like Ibra who was only effective as a pure striker. Rooney can pass, has technical skills and it is common knowledge that his shoot is also great. He reminds me of Eto'o and if Tito would use Rooney like Rijkaard and Pep used Eto'o he could add a lot to our team because we would be even more unpredictable and he could be the impulse we need when Tiki-Taka is useless against better teams (Bayern).
Rooney has played on the wings for us, but he is far better through the middle.
Going off some of the comments here you would think the player in question is run of the mill nobody playing amateur football, or something. Rooney has been a monumental player of immense skill for us over the last ten years, and for the longest time if he played well, the team did, and if he didn't then the rest of the team followed suit. He's been that influential.
That said I wouldn't be too sorry to see him leave at this point. He seems to be either at the very start of a decline, or he's crying out for a new challenge. Either way you could do a lot worse than add Rooney to your team, if even if you are Barcelona.