The Red Devils already captured Dutch winger Memphis Depay from PSV Eindhoven earlier in the summer and have since added Italian right-back Matteo Darmian from Torino, German star Bastian Schweinsteiger from Bayern Munich and French midfielder Morgan Schneiderlin from Southampton.
The quartet have cost a combined £78million but Rooney is aware that the players are of such high quality that they are sure to add plenty to the United squad.
"Bastian is a very experienced player who has won everything in the game and it's great that he has chosen to join us and left a team like Bayern Munich to come here," Rooney told MUTV.
"And Morgan as well – it's great to see Bastian, him, Matteo and Memphis all come in and give the squad a boost. It's exciting times and I'm sure over the next week or two it'll be great for us to get some training sessions in and get to know each other's games.
"Bastian speaks very good English so that's a boost for the squad, too. He's a fantastic player, he's shown that over the years and it's great that we've got him and I'm sure he'll be a good player for us. We had the day we first flew out when we first met Bastian and Morgan and they've settled in as well as they can do in a couple of days. It's great to have them with us."